Chapter 16 - Physical HazardsChapter 16 - Physical Hazards
In addition to the chemical hazards found in laboratories, there are also numerous physical hazards encountered by laboratory staff on a day-to-day basis. As with chemical hazards, having good awareness of these hazards, good preplanning, use of personal protective equipment and following basic safety rules can go a long way in preventing accidents involving physical hazards.
16.1 Electrical Safety16.1 Electrical Safety
Electricity travels in closed circuits, and its normal route is through a conductor. Shock occurs when the body becomes a part of the electric circuit. Electric shock can cause direct injuries such as electrical burns, arc burns, and thermal contact burns. It can also cause injuries of an indirect or secondary nature in which involuntary muscle reaction from the electric shock can cause bruises, bone fractures, and even death resulting from collisions or falls. Shock normally occurs in one of three ways.
The person must be in contact with ground and must contact with:
- Both wires of the electric circuit, or
- One wire of the energized circuit and the ground, or
- A metallic part that has become energized by being in contact with an energized wire.
The severity of the shock received when a person becomes a part of an electric circuit is affected by three primary factors:
- The amount of current flowing through the body (measured in amperes).
- The path of the current through the body.
- The length of time the body is in the circuit.
Other factors that may affect the severity of shock are the frequency of the current, the phase of the heart cycle when shock occurs, and the general health of the person prior to shock. The effects of an electrical shock can range from a barely perceptible tingle to immediate cardiac arrest. Although there are no absolute limits or even known values that show the exact injury from any given amperage, the table above shows the general relationship between the degree of injury and the amount of amperage for a 60-cycle hand-to-foot path of one second's duration of shock.
|1 Milliampere||Perception level. Just a faint tingle.|
|5 Milliamperes||Slight shock felt. Average individual can let go. However, strong involuntary reactions to shocks in this range can lead to injuries.|
|6-30 Milliamperes||Painful shock. Muscular control lost.|
|50-150 Milliamperes||Extreme pain, respiratory arrest, severe muscular contractions. Individual cannot let go. Death is possible.|
|1,000-4,300 Milliamperes||Ventricular fibrillation. Muscular contraction and nerve damage occur. Death is most likely.|
|10,000-Milliamperes||Cardiac arrest, severe burns and probable death.|
As this table illustrates, a difference of less than 100 milliamperes exists between a current that is barely perceptible and one that can kill. Muscular contraction caused by stimulation may not allow the victim to free himself/herself from the circuit, and the increased duration of exposure increases the dangers to the shock victim. For example, a current of 100 milliamperes for 3 seconds is equivalent to a current of 900 milliamperes applied for 0.03 seconds in causing fibrillation. The so-called low voltages can be extremely dangerous because, all other factors being equal, the degree of injury is proportional to the length of time the body is in the circuit. Simply put, low voltage does not mean low hazard.
In the event of an accident involving electricity, if the individual is down or unconscious, or not breathing: CALL Cornell University Police at 911 (607-255-1111 from a cell phone or off campus phone) immediately. If an individual must be physically removed from an electrical source, it is always best to eliminate the power source first (i.e.: switch off the circuit breaker) but time, or circumstance may not allow this option - be sure to use a nonconductive item such as a dry board. Failure to think and react properly could make you an additional victim. If the individual is not breathing and you have been trained in CPR, have someone call Cornell University Police and begin CPR IMMEDIATELY!
16.1.1 Common Electrical Hazards and Preventative Steps16.1.1 Common Electrical Hazards and Preventative Steps
Many common electrical hazards can be easily identified before a serious problem exists.
- Read and follow all equipment operating instructions for proper use. Ask yourself, "Do I have the skills, knowledge, tools, and experience to do this work safely?"
- Do not attempt electrical repairs unless you are a qualified electrical technician assigned to perform electrical work by your supervisor. Qualified individuals must receive training in safety related work practices and procedures, be able to recognize specific hazards associated with electrical energy, and be trained to understand the relationship between electrical hazards and possible injury. Fixed wiring may only be repaired or modified by Facilities Services.
- All electrical devices fabricated for experimental purposes must meet state and University construction and grounding requirements. Extension cords, power strips, and other purchased electrical equipment must be Underwriters Laboratories (UL) listed.
- Remove all jewelry before working with electricity. This includes rings, watches, bracelets, and necklaces.
- Determine appropriate personal protective equipment (PPE) based on potential hazards present. Before use, inspect safety glasses and gloves for signs of wear and tear, and other damage.
- Use insulated tools and testing equipment to work on electrical equipment. Use power tools that are double-insulated or that have Ground Fault Circuit Interrupters protecting the circuit. Do not use aluminum ladders while working with electricity; choose either wood or fiberglass.
- Do not work on energized circuits. The accidental or unexpected starting of electrical equipment can cause severe injury or death. Before any inspections or repairs are made, the current must be turned off at the switch box and the switch padlocked or tagged out in the off position. At the same time, the switch or controls of the machine or the other equipment being locked out of service should be securely tagged to show which equipment or circuits are being worked on. Test the equipment to make sure there is no residual energy before attempting to work on the circuit. Employees must follow the Cornell University lock-out/tag-out procedures.
- If you need additional power supply, the best solution is to have additional outlets installed by Facilities Services. Do not use extension cords or power strips ("power taps") as a substitute for permanent wiring.
- Extension cords and power strips may be used for experimental or developmental purposes on a temporary basis only. Extension cords can only be used for portable tools or equipment and must be unplugged after use. Do not use extension cords for fixed equipment such as computers, refrigerators/freezers, etc.; use a power strip in these cases. In general, the use of power strips is preferred over use of extension cords.
- Power strips must have a built-in overload protection (circuit breaker) and must not be connected to another power strip or extension cord (commonly referred to as daisy chained or piggy-backed). As mentioned above though, extension cords and power strips are not a substitute for permanent wiring.
- Ensure any power strips or extension cords are listed by a third-party testing laboratory, such as Underwriters Laboratory (UL). Make sure the extension cord thickness is at least as big as the electrical cord for the tool. For more information on extension cords, see the Consumer Product Safety Commission - Extension Cords Fact Sheet (CPSC Document #16).
- Inspect all electrical and extension cords for wear and tear. Pay particular attention near the plug and where the cord connects to the piece of equipment. If you discover a frayed electrical cord, contact your Building Coordinator for assistance. Do not use equipment having worn or damaged power cords, plugs, switches, receptacles, or cracked casings. Running electrical cords under doors or rugs, through windows, or through holes in walls is a common cause of frayed or damaged cords and plugs.
- Do not use 2-prong ungrounded electrical devices. All department-purchased electrical equipment must be 3-prong grounded with very limited exceptions.
- Never store flammable liquids near electrical equipment, even temporarily.
- Keep work areas clean and dry. Cluttered work areas and benches invite accidents and injuries. Good housekeeping and a well-planned layout of temporary wiring will reduce the dangers of fire, shock, and tripping hazards.
- Common scenarios that may indicate an electrical problem include: flickering lights, warm switches or receptacles, burning odors, sparking sounds when cords are moved, loose connections, frayed, cracked, or broken wires. If you notice any of these problems, have a qualified electrician address the issue immediately.
- To protect against electrical hazards and to respond to electrical emergencies it is important to identify the electrical panels that serve each room. Access to these panels must be unobstructed; a minimum of 3’ of clearance is required in front of every electrical panel. Each panel must have all the circuit breakers labeled as to what they control. Contact your Building Coordinator for assistance.
- When performing laboratory inspections, it is a good idea to verify the location of the power panel and to open the door to ensure any breakers that are missing have breaker caps in its place. If no breaker is present and no breaker cap is covering the hole, contact your Building Coordinator for assistance.
- Avoid operating or working with electrical equipment in a wet or damp environment. If you must work in a wet or damp environment, be sure your outlets or circuit breakers are Ground Fault Circuit Interrupter (GFCI) protected. Temporary GFCI plug adapters can also be used, but are not a substitute for GFCI outlets or circuit breakers.
Fuses, circuit breakers, and Ground-Fault Circuit Interrupters are three well-known examples of circuit protection devices.
- Fuses and circuit breakers are over-current devices that are placed in circuits to monitor the amount of current that the circuit will carry. They automatically open or break the circuit when the amount of the current flow becomes excessive and therefore unsafe. Fuses are designed to melt when too much current flows through them. Circuit breakers, on the other hand, are designed to trip open the circuit by electro-mechanical means.
- Fuses and circuit breakers are intended primarily for the protection of conductors and equipment. They prevent overheating of wires and components that might otherwise create hazards for operators.
- The Ground Fault Circuit Interrupter (GFCI) is designed to shut off electric power within as little as 1/40 of a second, thereby protecting the person, not just the equipment. It works by comparing the amount of current going to an electric device against the amount of current returning from the device along the circuit conductors. A fixed or portable GFCI should be used in high-risk areas such as wet locations and construction sites.
Entrances to rooms and other guarded locations containing exposed live parts must be marked with conspicuous warning signs forbidding unqualified persons to enter. Live parts of electric equipment operating at 50 volts or more must be guarded against accidental contact. Guarding of live parts may be accomplished by:
- Location in a room, vault, or similar enclosure accessible only to qualified persons.
- Use of permanent, substantial partitions or screens to exclude unqualified persons.
- Location on a suitable balcony, gallery, or platform elevated and arranged to exclude unqualified persons, or
- Elevation of 8 feet or more above the floor.
For additional information, see the following resources:
- OSHA Pamphlet 3075
- National Electric Code 2002
- National Fire Protection Association (NFPA) 70E
- UC Davis EHS
16.1.2 Safe Use of Electrophoresis Equipment16.1.2 Safe Use of Electrophoresis Equipment
Electrophoresis units present several possible hazards including electrical, chemical, and radiological hazards. All of these hazards need to be addressed before using the units. EHS has prepared these guidelines to assist researchers in safely operating electrophoresis units.
- Hazards associated with particular machines.
- How the safeguards provide protection and the hazards for which they are intended.
- How and why to use the safeguards.
- How and when safeguards can be removed and by whom.
- What to do if a safeguard is damaged, missing, or unable to provide adequate protection.
- Hazards to machine operators that can't be designed around must be shielded to protect the operator from injury or death. Guards, decals and labels which identify the danger must be kept in place whenever the machine is operated. Guards or shields removed for maintenance must be properly replaced before use. Moving parts present the greatest hazard because of the swiftness of their action and unforgiving and relentless motion
16.2 Machine Guarding16.2 Machine Guarding
Common machine hazards occurring around moving parts include:
Where two parts move together and at least one of the parts moves in a circle; also called mesh points, run-on points, and entry points. Examples include: Belt drives, chain drives, gear drives, and feed rolls.When shields cannot be provided, operators must avoid contact with hands or clothing in pinch point areas. Never attempt to service or unclog a machine while it is operating or the engine is running.
Any exposed component that rotates.Examples include: Rotating shafts such as a PTO shaft or shafts that protrude beyond bearings or sprockets. Watch components on rotating shafts, such as couplers, universal joints, keys, keyways, pins, or other fastening devices. Splined, square, and hexagon-shaped shafts are usually more dangerous than round shafts because the edges tend to grab fingers or clothing more easily than a round shaft, but round shafts may not be smooth and can also grab quickly. Once a finger, thread, article of clothing, or hair is caught it begins to wrap; pulling only causes the wrap to become tighter.
Where the edges of two moving parts move across one another or where a single sharp part moves with enough speed or force to cut soft material. Remember that crop cutting devices cannot be totally guarded to keep hands and feet out and still perform their intended function. Recognize the potential hazards of cutting and shear points on implements and equipment that are not designed to cut or shear. Guarding may not be feasible for these hazards.
Points that occur between two objects moving toward each other or one object moving toward a stationary object. Never stand between two objects moving toward one another. Use adequate blocking or lock-out devices when working under equipment.
Points where objects are pulled into equipment, usually for some type of processing. Machines are faster and stronger than people. Never attempt to hand-feed materials into moving feed rollers. Always stop the equipment before attempting to remove an item that has plugged a roller or that has become wrapped around a rotating shaft. Remember that guards cannot be provided for all situations - equipment must be able to function in the capacity for which it is designed. Freewheeling parts, rotating or moving parts that continue to move after the power is shut off are particularly dangerous because time delays are necessary before service can begin. Allow sufficient time for freewheeling parts to stop moving. Stay alert! Listen and Watch for Motion!
Any object that can become airborne because of moving parts. Keep shields in place to reduce the potential for thrown objects. Wear protective gear such as goggles to reduce the risk of personal injury if you cannot prevent particles from being thrown. All guards, shields or access doors must be in place when equipment is operating. Electrically powered equipment must have a lock-out control on the switch or an electrical switch, mechanical clutch or other positive shut-off device mounted directly on the equipment. Circuit interruption devices on an electric motor, such as circuit breakers or overload protection, must require manual reset to restart the motor.
16.3 Lighting16.3 Lighting
Having a properly lighted work area is essential to working safely. A couple of key points to remember about proper lighting:
- Lighting should be adequate for safe illumination of all work areas (100-200 lumens for laboratories). For more information, see the CU Design and Construction Standard 26500 – Interior Lighting.
- Light bulbs that are mounted low and susceptible to contact should be guarded.
- If the risk of electrocution exists when changing light bulbs, practice lock-out tag-out.
- For proper disposal of "universal waste" fluorescent bulbs, see light bulb recycling.
- As an energy conservation measure, please remember to turn off your lights when you leave your lab.
16.4 Compressed Gases16.4 Compressed Gases
Compressed gases are commonly used in laboratories.
- Gas cylinders may contain gases that are flammable, highly toxic, toxic, corrosive, asphyxiant, or oxidizing.
- A risk assessment, such as a POSHER (docx) review, may determine that a gas cabinet, leak detection, and an emergency shut off button in the hallway may be required.
- Unsecured cylinders can be tipped over, causing serious injury and damage. Impact can shear the valve from an uncapped cylinder, causing a catastrophic release of pressure leading to personal injury and extensive damage.
- Mechanical failure of the cylinder, cylinder valve, or regulator can result in rapid diffusion of the pressurized contents of the cylinder into the atmosphere; leading to explosion, fire, runaway reactions, or burst reaction vessels.
- A minimum 1 cubic foot/minute/square foot (cfm/ft2) of room ventilation is required for the storage and use of compressed gases due to the hazards listed in this chapter.
- In accordance with NFPA 704, gases or liquids having a hazard ranking of Health Class 3 or 4, Flammability Class 4, or Instability Class 3 or 4 that are carried in pressurized piping above 15 pounds per square inch gauge (psig) (103 kPa), an approved means of leak detection and emergency shutoff or excess flow control shall be provided.
Backflow prevention or check valves shall be provided where the backflow of the hazardous gas could create a hazardous condition or cause the unauthorized discharge of hazardous materials.
Piping, tubing, valves, fittings and related components shall be designed and fabricated from materials that are compatible with the material to be contained and shall be of adequate strength and durability to withstand the pressure, structural and seismic stress and exposure to which they are subject.
Use a restrictive flow orifice (RFO) or needle valve to restrict flow to only that needed for the experiment. Consider using a dilution of the gas that is suitable for the research, but falls outside of the code requirements.
- Manual valves or automatic remotely activated fail-safe emergency shutoff valves shall be installed on supply piping and tubing and provided with ready access at the following locations:
- The point of use.
- The tank, cylinder or bulk source.
Manual emergency shutoff valves and controls for remotely activated emergency shutoff valves shall be identified and the location shall have access clearly visible and indicated by means of a sign.
- Template (docx) for writing a Standard Operating Procedure- Use this template for developing protocols a specific hazardous gas system.
16.4.1 Safe Storage and Handling of Compressed Gas Cylinders16.4.1 Safe Storage and Handling of Compressed Gas Cylinders
- Restrain cylinders of all sizes by straps, chains, or a suitable stand to prevent them from falling;
- Keeps cylinders in storage upright, secure, and interlocked into a compact group;
- Do not use compressed gases in occupiable environmental chambers, cold rooms, or other similar stand-alone units. These typically do not provide outside air ventilation;
- Keep cylinders capped and the regulator off when not in use;
- Keep cylinders labeled with a full/in-use/empty tag.
- The contents of any compressed gas cylinder must be clearly identified. Labels on cylinders may be stenciled, stamped, or a label or tag attached to the cylinder. Do not rely on the color of the cylinder for identification because color-coding is not standardized and may vary with the manufacturer or supplier.
- For short term experiments using hazardous gases, always select the smallest returnable cylinder available. In cases where the gas will be used over an extended period of time (several months to more than one year), you should order a gas quantity that will last for three to six months;
- Some small cylinders, such as lecture bottles and cylinders of highly toxic gases, are not fitted with rupture devices and may explode if exposed to high temperatures;
- Do not store or use incompatible gases next to each other;
- Cylinders of oxygen must be stored at least 20 feet away from cylinders of any flammable gas.
- Isolate them by storing in a gas cabinets.
- Segregate full cylinders of low hazard gases from "empty" cylinders awaiting return to the vendor;
- Do not expose cylinders to temperatures higher than 50 ˚C (125 ˚F);
- Never place cylinders where they may become part of an electric circuit;
- Corrosive gases should be returned to the gas supplier within one year to avoid regulator and cylinder valve problems due to corrosion;
- Avoid areas that are damp or subject to other corrosive materials;
- When transporting cylinders:
- Always use a hand truck equipped with a chain or belt for securing the cylinder. Full size cylinders weigh up to 300 pounds.
- Make sure the protective cap covers the cylinder valve.
- Never transport a cylinder while a regulator is attached.
- Avoid riding in elevators with compressed gas cylinders. If this is necessary, consider using a buddy system to have one person send the properly secured cylinders on the elevator, while the other person waits at the floor by the elevator doors where the cylinders will arrive.
- Do not move compressed gas cylinders by carrying, rolling, sliding, or dragging them across the floor.
- Do not transport oxygen and combustible gases at the same time.
- Do not drop cylinders or permit them to strike anything violently.
16.4.2 Fume Hood Applications16.4.2 Fume Hood Applications
Fume hood applications: This does not apply to highly toxic and toxic compressed gases, in cylinders large than 20ft3 at STP due to the face velocity requirements.
- The smallest possible cylinder should be used for the experiment (a six-month bottle supply for routine use gases is appropriate, while smaller cylinder supplies are suggested for short term use);
- Cylinders of toxic and highly toxic gases that are 20 ft3 or smallerat NTP are allowed within fume hoods as long as there are no incompatible materials also used in the hood or storage of any items inside.
- Make an effort to obtain gas cylinders in returnable bottles;
- Order bottles with lowest cylinder pressure possible;
- Use a flow restricting orifice or needle valve to restrict flow to only that needed for the experiment;
- Consider using a dilution of the gas that is suitable for the research, but falls outside of the New York State code requirements;
- Place the cylinder in rear of the hood. High pressure leaks can readily escape the hood and capture is best in the rear of the hood;
- Assure all components in experiment can withstand full bottle pressure or incorporate pressure relief (run relief line into a hood slot);
- All gas lines connected to the hazardous gas source, including purge lines and gas supply lines, must be completely contained inside of the hood. If this is not possible, the cylinder must go into a gas cabinet.
16.4.3 Operation of Compressed Gas Cylinders16.4.3 Operation of Compressed Gas Cylinders
The cylinder valve hand wheel opens and closes the cylinder valve. The pressure relief valve is designed to keep a cylinder from exploding in case of fire or extreme temperature. Cylinders of very toxic gases do not have a pressure relief valve, but they are constructed with special safety features. The valve outlet connection is the joint used to attach the regulator. The pressure regulator is attached to the valve outlet connector in order to reduce the gas flow to a working level. The Compressed Gas Association has intentionally made certain types of regulators incompatible with certain valve outlet connections to avoid accidental mixing of gases that react with each other. Gases should always be used with the appropriate regulator. Do not use adaptors with regulators. The cylinder connection is a metal-to-metal pressure seal. Make sure the curved mating surfaces are clean before attaching a regulator to a cylinder. Do not use Teflon tape on the threaded parts, because this may actually cause the metal seal not to form properly. Always leak test the connection.
Here is a link to the Airgas material compatibility chart: http://airgassgcatalog.com/catalog/ap020.pdf as well as the available excess flow valves: http://airgassgcatalog.com/catalog/E113_TAG_096.pdf
Basic Operating guidelines include:
- Make sure that the cylinder is secured.
- Attach the proper regulator to the cylinder. If the regulator does not fit, it may not be suitable for the gas you are using.
- Attach the appropriate hose connections to the flow control valve. Secure any tubing with clamps so that it will not whip around when pressure is turned on. Use suitable materials for connections; toxic and corrosive gases require connections made of special materials.
- Install a trap between the regulator and the reaction mixture to avoid backflow into the cylinder.
- To prevent a surge of pressure, turn the delivery pressure adjusting screw counterclockwise until it turns freely and then close the flow control valve.
- Slowly open the cylinder valve hand wheel until the cylinder pressure gauge reads the cylinder pressure.
- With the flow control valve closed, turn the delivery pressure screw clockwise until the delivery pressure gauge reads the desired pressure.
- Adjust the gas flow to the system by using the flow control valve or another flow control device between the regulator and the experiment.
- After an experiment is completed, turn the cylinder valve off first, and then allow gas to bleed from the regulator. When both gauges read “zero”, remove the regulator and replace the protective cap on the cylinder head.
- When the cylinder is empty, mark it as “Empty”, and store empty cylinders separate from full cylinders.
- Attach a “Full/In Use/Empty” tag to all of your cylinders, these tags are perforated and can be obtained from the gas cylinder vendor.
Precautions to follow:
- Use a regulator only with gas for which it is intended. The use of adaptors or homemade connectors has caused serious and even fatal accidents.
- Toxic gases should be purchased with a flow-limiting orifice.
- When using more than one gas, be sure to install one-way flow valves from each cylinder to prevent mixing. Otherwise accidental mixing can cause contamination of a cylinder.
- Do not attempt to put any gas into a commercial gas cylinder.
- Do not allow a cylinder to become completely empty. Leave at least 25 psi of residual gas to avoid contamination of the cylinder by reverse flow.
- Do not tamper with or use force on a cylinder valve.
16.4.4 Return of Cylinders16.4.4 Return of Cylinders
Disposal of cylinders and lecture bottles is expensive, especially if the contents are unknown.
- Make sure that all cylinders and lecture bottles are labeled and included in your chemical inventory. Before you place an order for a cylinder or lecture bottle, determine if the manufacturer will take back the cylinder or lecture bottle when it becomes empty.
- If at all possible, only order from manufacturers who will accept cylinders or lecture bottles for return.
16.4.5 Hazards of Specific Gases16.4.5 Hazards of Specific Gases
- Inert Gases - These can cause asphyxiation by displacing the air necessary for the support of life.
- Examples: Helium, Argon, Nitrogen
- Cryogens are capable of causing freezing burns, frostbite, and destruction of tissue.
- Cryogenic Liquids - Cryogenic liquids are extremely cold and their vapors can rapidly freeze human tissue.
- Boiling and splashing will occur when the cryogen contacts warm objects.
- Can cause common materials such as plastic and rubber to become brittle and fracture under stress.
- Liquid to gas expansion ratio: one volume of liquid nitrogen will vaporize and expand to about 700 times that volume, as a gas, and thus can build up tremendous pressures in a closed system. Therefore, dispensing areas need to be well ventilated. Avoid storing cryogenics in cold rooms, environmental chambers, and other areas with poor ventilation. If necessary, install an oxygen monitor/oxygen deficiency alarm and/or toxic gas monitor before working with these materials in confined areas.
- Oxidizers- Oxidizers vigorously accelerate combustion; therefore keep away from all flammable and organic materials. Greasy and oily materials should never be stored around oxygen. Oil or grease should never be applied to fittings or connectors.
- Examples: Oxygen, Chlorine
- Flammable Gases - Flammable gases are easily ignited by heat, sparks, or flames, and may form explosive mixtures with air. Vapors from liquefied gas often are heavier than air, and may spread along the ground and travel to a source of ignition and result in a flashback fire.
- Examples: Methane, Propane, Hydrogen, Acetylene, flammable gas mixtures.
- Flammable gases present serious fire and explosion hazards.
- Do not store near open flames or other sources of ignition.
- Cylinders containing Acetylene should never be stored on their side.
- Corrosive Gases- Corrosive gases readily attack the skin, mucous membranes, and eyes. Some corrosive gases are also toxic.
- Examples: Chlorine, Hydrogen Chloride, Ammonia
- There can be an accelerated corrosion of materials in the presence of moisture.
- Due to the corrosive nature of the gases, corrosive cylinders should only be kept on hand for 6 months (up to one year maximum). Only order the smallest size needed for your experiments
- Poison Gases- Poison gases are extremely toxic and present a serious hazard to laboratory staff.
- Examples: Arsine, Phosphine, Phosgene
- Poisonous gases require special ventilation systems and equipment and must only be used by properly trained experts. There are also special building code regulations that must be followed with regard to quantities kept on hand and storage.
- The purchase and use of poisonous gases require prior approval from EHS. Contact the Chemical Hygiene Officer at 607-255-8200.
16.4.6 Gas Generators16.4.6 Gas Generators
Gas Generators for Nitrogen or Hydrogen Gas
Gas generators are an alternative to having compressed gas cylinders in the laboratory. These provide high purity nitrogen or hydrogen and can be connected to lab equipment often without the New York State code implications due to the small quantities that are being stored.
Hydrogen Gas Generators:
- Produce gas on demand via electrolysis of water:
- Store up to 100 ml of gas:
- Require 15 megohm quality deionized water;
- Outlet pressures (psig) and flow rate requirements must be determined for installation.
Nitrogen Gas Generator:
- Produce gas via filtration from the air:
- This is a continuous supply;
- Have varying delivery flow rates. Typically maximum flows are 35 to 70 Liters/minute;
- Operate at maximum pressures of 116 psi (8 bar).
At flow rate requirements above 15 psi (1.05 bar), the Authority Having Jurisdiction may require gas detection. At lower flow rates they may waive this requirement. An engineering review is necessary. These generators do add to the heat load of the room in which they are located.
16.5 Battery Charging16.5 Battery Charging
Lead acid batteries contain corrosive liquids and also generate Hydrogen gas during charging which poses an explosion hazard. The following guidelines should be followed for battery charging areas:
- A “No smoking” sign should be posted.
- Before working, remove all jewelry from hands and arms and any dangling jewelry to prevent accidental contact with battery connections (this can cause sparks which can ignite vapors).
- Always wear appropriate PPE such as rubber or synthetic aprons, splash goggles (ideally in combination with a face shield), and thick Neoprene, Viton, or Butyl gloves.
- A plumbed emergency eyewash station must be readily available near the station (please note, hand held eyewash bottles do not meet this criteria.)
- A class B rated fire extinguisher needs to be readily available. If none is available, contact EHS at 607-255-8200.
- Ensure there is adequate ventilation available to prevent the buildup of potentially flammable and explosive gases.
- Keep all ignition sources away from the area.
- Stand clear of batteries while charging.
- Keep vent caps tight and level.
- Only use the appropriate equipment for charging.
- Store unused batteries in secondary containment to prevent spills.
- Have an acid spill kit available. The waste from a spill may contain lead and neutralized wastes may be toxic. Contact EHS at 607-255-8200 for hazardous waste disposal.
- Properly dispose of your used batteries.
16.6 Heat and Heating Devices16.6 Heat and Heating Devices
Heat hazards within laboratories can occur from a number of sources; however, there are some simple guidelines that can be followed to prevent heat related injuries. These guidelines include:
- Heating devices should be set up on a sturdy fixture and away from any ignitable materials (such as flammable solvents, paper products and other combustibles). Do not leave open flames (from Bunsen burners) unattended.
- Heating devices should not be installed near drench showers or other water spraying apparatus due to electrical shock concerns and potential splattering of hot water.
- Heating devices should have a backup power cutoff or temperature controllers to prevent overheating. If a backup controller is used, an alarm should notify the user that the main controller has failed.
- Provisions should be included in processes to make sure reaction temperatures do not cause violent reactions and a means to cool the dangerous reactions should be available.
- Post signs to warn people of the heat hazard to prevent burns.
When using ovens, the follow additional guidelines should be followed:
- Heat generated should be adequately removed from the area.
- If toxic, flammable, or otherwise hazardous chemicals are evolved from the oven, then only use ovens with a single pass through design where air is ventilated out of the lab and the exhausted air is not allowed to come into contact with electrical components or heating elements.
- Heating flammables should only be done with a heating mantle or steam bath.
When using heating baths, these additional guidelines should be followed:
- Heating baths should be durable and set up with firm support.
- Since combustible liquids are often used in heat baths, the thermostat should be set so the temperature never rises above the flash point of the liquid. Check the SDS for the chemical to determine the flashpoint. Compare that flashpoint with the expected temperature of the reaction to gauge risk of starting a fire.
16.6.1 Heat Stress16.6.1 Heat Stress
Another form of heat hazard occurs when working in a high heat area. Under certain conditions, your body might have trouble regulating its temperature. If your body cannot regulate its temperature, it overheats and suffers some degree of heat stress. This can occur very suddenly and, if left unrecognized and untreated, can lead to very serious health affects.
Heat stress disorders range from mild disorders such as fainting, cramps, or prickly heat to more dangerous disorders such as heat exhaustion or heat stroke. Symptoms of mild to moderate heat stress can include: sweating, clammy skin, fatigue, decreased strength, loss of coordination and muscle control, dizziness, nausea, and irritability. You should move the victim to a cool place and give plenty of fluids. Place cool compresses on forehead, neck, and under their armpits.
Heat stroke is a medical emergency. It can cause permanent damage to the brain and vital organs, or even death. Heat stroke can occur suddenly, with little warning. Symptoms of heat stroke may include: no sweating (in some cases victim may sweat profusely), high temperature (103? or more), red, hot, and dry skin, rapid and strong pulse, throbbing headache, dizziness, nausea, convulsions, delirious behavior, unconsciousness, or coma.
In the case of heat stroke, call 911 & get medical assistance ASAP! In the meantime, you should move the victim to a cool place, cool the person quickly by sponging with cool water and fanning, and offer a conscious person 1/2 glass of water every 15 minutes. There are a number of factors that affect your body’s temperature regulation:
- Radiant heat sources such as the sun or a furnace.
- Increased humidity causes decreased sweat evaporation.
- Decreased air movement causes decreased sweat evaporation.
- As ambient temperature rises, your body temperature rises and its ability to regulate decreases.
- You should be especially careful if:
- You just started a job involving physical work in a hot environment.
- You are ill, overweight, physically unfit, or on medication that can cause dehydration.
- You have been drinking alcohol.
- You have had a previous heat stress disorder.
In order to prevent heat stress, please follow these recommendations:
- Acclimatize your body to the heat. Gradually increase the time you spend in the heat. Most people acclimatize to warmer temperatures in 4-7 days. Acclimatization is lost when you have been away from the heat for one week or more. When you return, you must repeat the acclimatization process.
- Drink at least 4-8 ounces of fluid every 15-20 minutes to maintain proper balance during hot and/or humid environments. THIRST IS NOT A GOOD INDICATOR OF DEHYDRATION. Fluid intake must continue until well after thirst has been quenched.
- During prolonged heat exposure or heavy workload, a carbohydrate-electrolyte beverage is beneficial.
- Alternate work and rest cycles to prevent an overexposure to heat. Rest cycles should include relocation to a cooler environment.
- Perform the heaviest workloads in the cooler part of the day.
- There should be no alcohol consumption during periods of high heat exposure.
- Eat light, preferably cold meals. Fatty foods are harder to digest in hot weather.
16.7 Cold Traps16.7 Cold Traps
- Because many chemicals captured in cold traps are hazardous, care should be taken and appropriate protective equipment should be worn when handling these chemicals. Hazards include flammability, toxicity, and cryogenic temperatures, which can burn the skin.
- If liquid nitrogen is used, the chamber should be evacuated before charging the system with coolant. Since oxygen in air has a higher boiling point than nitrogen, liquid oxygen can be produced and cause an explosion hazard.
- Boiling and splashing generally occur when charging (cooling) a warm container, so stand clear and wear appropriate protective equipment. Items should be added slowly and in small amounts to minimize splash.
- A blue tint to liquid nitrogen indicates contamination with oxygen and represents an explosion hazard. Contaminated liquid nitrogen should be disposed of appropriately.
- If working under vacuum see the “reduced pressure” section.
- See “cryogenics” for safety advice when working with cryogenic materials.
16.8 Autoclaves16.8 Autoclaves
Autoclaves have the following potential hazards:
- Heat, steam, and pressure.
- Thermal burns from steam and hot liquids.
- Cuts from exploding glass.
Some general safety guidelines to follow when using autoclaves:
- All users should be given training in proper operating procedures for using the autoclave.
- Read the owner’s manual before using the autoclave for the first time.
- Operating instructions should be posted near the autoclave.
- Follow the manufacturer’s directions for loading the autoclave.
- Be sure to close and latch the autoclave door.
- Some kinds of bottles containing liquids can crack in the autoclave, or when they are removed from the autoclave. Use a tray to provide secondary containment in case of a spill, and add a little water to the tray to ensure even heating.
- Only fill bottles half way to allow for liquid expansion and loosen screw caps on bottles and tubes of liquid before autoclaving, to prevent them from shattering.
- Do not overload the autoclave compartment and allow for enough space between items for the steam to circulate.
- Be aware that liquids, especially in large quantities, can be superheated when the autoclave is opened. Jarring them may cause sudden boiling, and result in burns.
- At the end of the run, open the autoclave slowly: first open the door only a crack to let any steam escape slowly for several minutes, and then open all the way. Opening the door suddenly can scald a bare hand, arm, or face.
- Wait at least five minutes after opening the door before removing items.
- Large flasks or bottles of liquid removed immediately from the autoclave can cause serious burns by scalding if they break in your hands. Immediately transfer hot items with liquid to a cart; never carry in your hands.
- Wear appropriate PPE, including eye protection and insulating heat-resistant gloves.
16.9 Centrifuges16.9 Centrifuges
Some general safety guidelines to follow when using centrifuges:
- Be familiar with the operating procedures written by the manufacturer. Keep the operating manual near the unit for easy reference. If necessary contact the manufacturer to replace lost manuals.
- Handle, load, clean, and inspect rotors as recommended by the manufacturer.
- Pay careful attention to instructions on balancing samples -- tolerances for balancing are often very restricted. Check the condition of tubes and bottles. Make sure you have secured the lid to the rotor and the rotor to the centrifuge.
- Maintain a logbook of rotor use for each rotor, recording the speed and length of time for each use.
- To avoid catastrophic rotor failure, many types of rotors must be "de-rated" (limited to a maximum rotation speed that is less than the maximum rotation speed specified for the rotor when it is new) after a specified amount of use, and eventually taken out of service and discarded.
- Use only the types of rotors that are specifically approved for use in a given centrifuge unit.
- Maintain the centrifuge in good condition. Broken door latches and other problems should be repaired before using the centrifuge.
- Whenever centrifuging biohazardous materials, always load and unload the centrifuge rotor in a Biosafety cabinet.
16.9.1 Centrifuge Rotor Care16.9.1 Centrifuge Rotor Care
Basic centrifuge rotor care includes:
- Keep the rotor clean and dry, to prevent corrosion.
- Remove adapters after use and inspect for corrosion.
- Store the rotor upside down, in a warm, dry place to prevent condensation in the tubes.
- Read and follow the recommendations in the manual regarding:
- Regular cleaning
- Routine inspection
- Regular polishing
- Lubricating O-rings
- Decontaminating the rotor after use with radioactive or biological materials
- Remove any rotor from use that has been dropped or shows any sign of defect, and report it to a manufacturer’s representative for inspection.
There is a description of an accident that occurred at Cornell and how to prevent centrifuge accidents on the Centrifuge Accident webpage.
16.10 Cryogenic Material Safety16.10 Cryogenic Material Safety
According to the Compressed Gas Association, a cryogenic fluid is a material that has a boiling point of less than -130°F (-90°C). Examples of cryogenic materials include the liquids nitrogen, argon, and helium, and solid carbon dioxide (dry ice). Hazards associated with cryogenic fluids include:
Extreme Low Temperature - These liquids and their boiled off vapors are extremely cold and can cause severe cold contact burns. They also make many materials brittle, such as the epoxy or phenolic resin that laboratory benchtops and sinks are made of.
Asphyxiation - When liquid and solid cryogenic materials vaporize they greatly expand, some by a factor of ~700:1. This displaces oxygen and creates an oxygen depletion hazard. This is especially dangerous when confined in poorly ventilated space like an elevator.
Oxygen makes up 20.9% of the air we breathe. The environment is considered to be oxygen deficient below 19.5%. Two breaths of air with no oxygen can be enough to render a person unconscious.
Typical background levels of carbon dioxide are about 400 ppm. Vaporization of even small quantities of Dry Ice in an unventilated area can exceed the permissible exposure limit of 5000 ppm.
Exposure to oxygen-deficient atmospheres produce dizziness, nausea, vomiting, loss of consciousness, and death. Such symptoms may occur in seconds without warning.
Death may result from errors in judgment, confusion, or loss of consciousness that prevents self-rescue. Working with cryogenic substances in confined spaces, such as walk-in coolers, can be especially hazardous. Where cryogenic materials are used, a hazard assessment is required to determine the potential for an oxygen-deficient condition. Controls such as ventilation and/or gas detection systems may be required to safeguard employees. Asphyxiation and chemical toxicity are hazards encountered when entering an area that has been used to store cryogenic liquids if proper ventilation/purging techniques are not employed.
Toxicity - Many of the commonly used cryogenic gases are considered to be of low toxicity, but still pose a hazard from asphyxiation. Check the properties of the gases you are using because some gases are toxic, for example, Carbon monoxide, Fluorine, and Nitrous oxide.
Flammability and Explosion - Fire or explosion may result from the evaporation and vapor buildup of flammable gases such as hydrogen, carbon monoxide, or methane. Liquid oxygen, while not itself a flammable gas, can combine with combustible materials and greatly accelerate combustion.
Oxygen clings to clothing and cloth items, and presents an acute fire hazard.
High Pressure - In cryogenic systems, high pressures are obtained by gas compression during refrigeration. Warm temperatures surrounding containers cause a constant expansion of the liquid as it turns back into gas. Sudden release through a rupture or break in a line may be violent. Over- pressurization of cryogenic equipment can occur due to improper venting and expansion during the phase change from liquid to gas. All cryogenic fluids produce large volumes of gas when they vaporize.
Materials and Construction Hazards - The selection of materials calls for consideration of the effects of low temperatures on the properties of those materials. Some materials become brittle at super low temperatures. Brittle materials fracture easily and can result in almost instantaneous material failure.
Low temperature equipment can also fail due to thermal stresses caused by differential thermal contraction of the materials. Over-pressurization of cryogenic equipment can occur due to the phase change from liquid to gas if not vented properly.
16.10.1 Cryogenic Safety Guidelines16.10.1 Cryogenic Safety Guidelines
Personnel who are responsible for any cryogenic equipment must conduct a safety review prior to the commencement of operation of the equipment. Supplementary safety reviews must follow any system modification to ensure that no potentially hazardous condition is overlooked or created, and that updated operational and safety procedures remain adequate.
Clothing and Personal Protective Equipment
Wear the appropriate clothing and PPE when working and transferring cryogenic materials.
- Safety glasses are a minimum to be worn during the transfer and normal handling of cryogenic fluids. Face shields must be worn over safety glasses if there is the potential for splashing in the face, such as filling dewars.
- Loose fitting, heavy leather or other insulating protective gloves must be worn when handling cryogenic fluids.
- Shirt sleeves should be rolled down and buttoned over glove cuffs, or equivalent protection, such as a lab coat, should be worn in order to prevent liquid from spraying or spilling inside the gloves. Do not wear short sleeves when working with cryogenic liquids.
- Long pants without cuffs and that don’t expose skin must be worn.
- Shoes that cover the feet are required. These must not allow cryogenic materials to come into contact with skin. Shoes must not allow a cryogenic liquid to become trapped in the material or soak in liquid in the event of a spill. Leather or other non-woven material is recommended.
Cryogenic fluids must be handled and stored only in containers and piping systems specifically designed to withstand the extremely cold temperatures, and in accordance with applicable standards, procedures, and proven safe practices, and be based on the specific cryogen.
Transfer operations involving open cryogenic containers such as dewars must be conducted slowly to minimize boiling and splashing of the cryogenic fluid. Transfer of cryogenic fluids from open containers must occur below chest level of the person pouring the liquid and on a steady surface.
Only conduct such operations in well-ventilated areas to prevent possible gas or vapor accumulation that may produce an oxygen-deficient atmosphere and lead to asphyxiation. If this is not possible, an oxygen monitor must be installed.
Small spaces, environmental chambers, and cold rooms often do not have sufficient exhaust ventilation to support storage and use of cryogenic materials. Contact EHS with any questions and to conduct a risk assessment.
All cryogenic systems, including piping, must be equipped with pressure relief devices to prevent excessive pressure build-up. If a container vents continuously, shows signs of blockage by not venting at all, or there is frost buildup on the outside, which indicates that there is loss of vacuum, do the following:
Do not attempt to remove a blockage;
Move the vessel to a remote location or notify others of the problem;
Contact the supplier for assistance with the vessel.
- The caps of liquid nitrogen dewars are designed to fit snugly to contain the liquid nitrogen, but also allow the periodic venting that will occur to prevent over pressurization of the vessel. Do not ever attempt to seal the caps of liquid nitrogen dewars. Doing so can present a significant hazard of over pressurization that could rupture the container and cause splashes of liquid nitrogen. Depending on the amount of liquid nitrogen that may be spilled, this could cause an oxygen deficient atmosphere within a laboratory due to the sudden release and vaporization of the cryogenic liquid.
- In the event of a spill, oxygen deficiency or a flammable atmosphere will exist beyond any visible fog cloud.
Emergency treatment if skin or eyes come into contact with cryogenic liquid or vapor is as follows:
- If the cryogenic fluid comes in contact with the skin or eyes, flush the affected area with generous quantities of cold water. Never use dry heat. Splashes on bare skin cause a stinging sensation, but in general are not harmful.
- If clothing becomes soaked with liquid, it should be removed as quickly as possible and the affected area should be flooded with water as above.
- Where clothing has frozen to the underlying skin, cold water should be poured on the area, but no attempt should be made to remove the clothing until it is completely free.
- If inhalation of the cold vapors has occurred, move the person to warm, fresh air. The person may be suffering from frostbite tissue in their throat and lungs, and also asphyxia.
- Do NOT rub frostbitten skin as tissue damage may occur. Place in a warm bath that is not above 105°F (40°C).
- For emergencies: Call 607-255-1111 from a cell phone or 911 from a campus phone.
- Complete an Injury/Illness Report
16.10.2 Cryogenic Chemical Specific Information16.10.2 Cryogenic Chemical Specific Information
Liquid helium must be transferred via helium pressurization in properly designed transfer lines. A major safety hazard may occur if liquid helium comes in contact with air. Air solidifies in contact with liquid helium, and precautions must be taken when transferring liquid helium from one vessel to another or when venting. Over-pressurization and rupture of the container may result. All liquid helium containers must be equipped with a pressure-relief device. The latent heat of vaporization of liquid helium is extremely low (20.5 J/gm); therefore, small heat leaks can cause rapid pressure rises.
Since the boiling point of liquid nitrogen is below that of liquid oxygen, it is possible for oxygen to condense on any surface cooled by liquid nitrogen. If the system is subsequently closed and the liquid nitrogen removed, the evaporation of the condensed oxygen may over-pressurize the equipment or cause a chemical explosion if exposed to combustible materials, e.g., the oil in a rotary vacuum pump. In addition, if the mixture is exposed to radiation ozone is formed, which freezes into ice and is very unstable. An explosion can result if this ice is disturbed. For this reason, air should not be admitted to enclosed equipment that is below the boiling point of oxygen unless specifically required by a written procedure.
Any transfer operations involving open containers such as wide-mouth dewars must be conducted slowly to minimize boiling and splashing of liquid nitrogen. The transfer of liquid nitrogen from open containers must occur below chest level of the person pouring the liquid.
If liquid nitrogen or helium traps are used to remove condensable gas impurities from a vacuum system that may be closed off by valves, the condensed gases will be released when the trap warms up.
Adequate means for relieving resultant build-up of pressure must be provided.
Any proposal for the use of liquid hydrogen must obtain prior approval and undergo an EHS risk assessment and engineering code review.
- Because of its wide flammability range and ease of ignition, special safety measures must be invoked when using liquid hydrogen.
- Liquid hydrogen must be transferred by helium pressurization in properly designed transfer lines to avoid contact with air. Properly constructed and certified vacuum insulated transfer lines should be used.
- Rooms where flammable gas is used must be positively pressurized.
- Only trained personnel familiar with liquid hydrogen properties, equipment, and operating procedures are permitted to perform transfer operations. Transfer lines in liquid hydrogen service must be purged with helium or gaseous hydrogen, with proper precautions, before using.
The safety philosophy in the use of liquid hydrogen can be summarized as the following:
- Isolation of the experiment. Provision of adequate ventilation.
- Exclusion of ignition sources plus system grounding/bonding to prevent static charge build-up. Containment in helium purged vessels.
- Efficient monitoring for hydrogen leakage.
- Limiting the amount of hydrogen cryo-pumped in the vacuum system.
Any proposal to use liquid oxygen must obtain prior approval and undergo an EHS risk assessment and engineering code review.
- Liquid oxygen does not burn; however, it greatly accelerates fire. Adequate ventilation to avoid oxygen enrichment of the air is necessary.
- A room with combustible materials, oils and grease, electrical equipment, an ignition source, or flammable liquids and vapors should be avoided.
- OSHA defines an oxygen enriched atmosphere as being more than 22% oxygen. Oxygen enriched atmospheres present a significant fire and explosion risk.
- In the event of saturation of clothing with liquid oxygen, stay away from ignition sources for at least 30 minutes or change clothing.
16.10.3 Handling Cryogenic Materials on Elevators16.10.3 Handling Cryogenic Materials on Elevators
There is typically little or no fresh air supplied inside of elevators. Cryogenic materials displace air. To avoid a situation in which there is insufficient breathable air, the following are expected in Cornell buildings:
- Quantities up to 5 liters of a cryogenic material are acceptable to travel in an elevator accompanied by people.
- Quantities greater than 5 liters of cryogenic material must be transported on an elevator unaccompanied as it travels between floors. Do NOT transport a pressurized container in an elevator with any person/s in the elevator car.
- Transport in a freight elevator, if possible.
- Post a sign on the vessel in the elevator reading “DO NOT ENTER – CRYOGEN ASPHYXIATION HAZARD” to warn potential passengers.
- Have another person available on the receiving floor to take the container off the elevator at its destination.
- Beware of tipping the vessel while moving on or off the elevator. This is especially important of uncapped dewars of liquid nitrogen.
- Wear insulated cryogen safety gloves, safety goggles, long shirt, and long pants without cuffs. Wear footwear that will not soak in the liquid in case of a spill (e.g. leather instead of woven mesh).
- In case of a spill of any quantity on an elevator:
- Press the button to stop at the nearest floor;
- Block the elevator door open so that it doesn't move to the next floor;
- Call 607-255-1111 from a cell phone or 911 from a campus phone.
16.11 Extractions and Distillations16.11 Extractions and Distillations
- Do not attempt to extract a solution until it is cooler than the boiling point of the extractant due to the risk of overpressurization, which could cause the vessel to burst.
- When a volatile solvent is used, the solution should be swirled and vented repeatedly to reduce pressure before separation.
- When opening the stopcock, your hand should keep the plug firmly in place.
- The stopcock should be lubricated.
- Vent funnels away from ignition sources and people, preferably into a hood.
- Keep volumes small to reduce the risk of overpressure and if large volumes are needed, break them up into smaller batches.
- Avoid bumping (sudden boiling) since the force can break apart the apparatus and result in splashes. Bumping can be avoided by even heating, such as using a heat mantle. Also, stirring can prevent bumping. Boiling stones can be used only if the process is at atmospheric pressure.
- Do not add solid items such as boiling stones to liquid that is near boiling since it may result in the liquid boiling over spontaneously.
- Organic compounds should never be allowed to boil to dryness unless they are known to be free of peroxides, which can result in an explosion hazard.
Reduced pressure distillation
- Do not overheat the liquid. Superheating can result in decomposition and uncontrolled reactions.
- Superheating and bumping often occur at reduced pressures so it is especially important to abide by the previous point on bumping and to ensure even, controlled heating. Inserting a nitrogen bleed tube may help alleviate this issue.
- Evacuate the assembly gradually to minimize bumping.
- Allow the system to cool and then slowly bleed in air. Air can cause an explosion in a hot system (pure nitrogen is preferable to air for cooling).
- See “reduced pressure” for vacuum conditions.
16.12 Glass Under Vacuum16.12 Glass Under Vacuum
Some general guidelines for glass under vacuum include:
- Inspect glassware that will be used for reduced pressure to make sure there are no defects such as chips or cracks that may compromise its integrity.
- Only glassware that is approved for low pressure should be used. Never use a flat bottom flask (unless it is a heavy walled filter flask) or other thin walled flask that are not appropriate to handle low pressure.
- Use a shield between the user and any glass under vacuum or wrap the glass with tape to contain any glass in the event of an implosion.
- Cold traps should be used to prevent pump oil from being contaminated which can create a hazardous waste.
- Pump exhaust should be vented into a hood when possible.
- Ensure all belts and other moving parts are properly guarded.
- Whenever working on or servicing vacuum pumps, be sure to follow appropriate lock-out procedures.
16.13 Glassware Washing16.13 Glassware Washing
In most cases laboratory glassware can be cleaned effectively by using detergents and water. In some cases it may be necessary to use strong chemicals for cleaning glassware. Strong acids should be avoided unless necessary. In particular, Chromic acid should not be used due to its toxicity and disposal concerns. One product that may be substituted for Chromic acid is “Nochromix Reagent”. The Fisher catalog describes this material as: “Nochromix Reagent. Inorganic oxidizer chemically cleans glassware. Contains no metal ions. Rinses freely—leaving no metal residue, making this product valuable for trace analysis, enzymology, and tissue culture work. (Mix with sulfuric acid).” Unused Nochromix Reagent can be neutralized to a pH between 5.5 and 9.5 and drain disposed. Acid/base baths should have appropriate labeling and secondary containment. Additionally a Standard Operating Procedure (SOP), proper personal protective equipment (PPE), and spill materials should be available. Proper disposal for spent acid/base bath contents is neutralization and drain disposal.
When handling glassware, check for cracks and chips before washing, autoclaving or using it. Dispose of chipped and broken glassware immediately in an approved collection unit. DO NOT put broken glassware in the regular trash. Handle glassware with care – avoid impacts, scratches or intense heating of glassware. Make sure you use the appropriate labware for the procedures and chemicals.
Use care when inserting glass tubing into stoppers:
- Use glass tubing that has been fire-polished
- Lubricate the glass
- Protect your hands with heavy gloves
If your department/building has a glass washing service there are certain protocols that must be followed before sending the glassware to be washed. It is the responsibility of the lab to empty and rinse all glassware before it leaves the lab. Although the contents may not be hazardous, the washroom support staff cannot be certain of the appropriate PPE to wear, disposal regulations or possible incompatibilities with items received from other researchers. Be aware that labeling for lab personnel is not sufficient for areas outside the lab as per the OSHA Hazard Communication Standard. It is the responsibility of the glassware washing staff to reject or return glassware that is not acceptable due to breakage or containing chemicals. For this reason, glassware should be labeled with the name of the person who is responsible for it.
16.14 General Equipment Set Up16.14 General Equipment Set Up
The following recommended laboratory techniques for general equipment set up was taken from the American Chemical Society’s booklet – Safety in Academic Chemistry Laboratories.
16.14.1 Glassware and Plasticware16.14.1 Glassware and Plasticware
- Borosilicate glassware (i.e. pyrex) is recommended for all lab glassware, except for special experiments using UV or other light sources. Soft glass should only be used for things such as reagent bottles, measuring equipment, stirring rods and tubing.
- Any glass equipment being evacuated, such as suction flasks, should be specially designed with heavy walls. Dewar flasks and large vacuum vessels should be taped or guarded in case of flying glass from an implosion. Household thermos bottles have thin walls and are not acceptable substitutes for lab Dewar flasks.
- Glass containers containing hazardous chemicals should be transported in rubber bottle carriers or buckets to protect them from breakage and contain any spills or leaks. It is recommended to transport plastic containers this way as well since they also can break or leak.
16.14.2 Preparation of Glass Tubing and Stoppers16.14.2 Preparation of Glass Tubing and Stoppers
- To cut glass tubing:
- Hold the tube against a firm support and make one firm quick stroke with a sharp triangular file or glass cutter to score the glass long enough to extend approximately one third around the circumference.
- Cover the tubing with cloth and hold the tubing in both hands away from the body. Place thumbs on the tubing opposite the nick 2 to 3 cm and extended toward each other.
- Push out on the tubing with the thumbs as you pull the sections apart, but do not deliberately bend the glass with the hands. If the tubing does not break, re-score the tube in the same place and try again. Be careful to not contact anyone nearby with your motion or with long pieces of tubing.
- All glass tubing, including stir rods, should be fire polished before use. Unpolished tubing can cut skin as well as inhibit insertion into stoppers. After polishing or bending glass, give ample time for it to cool before grasping it.
- When drilling a stopper:
- Use only a sharp borer one size smaller than that which will just slip over the tube to be inserted. For rubber stoppers, lubricate with water or glycerol. Holes should be bored by slicing through the stopper, twisting with moderate forward pressure, grasping the stopper only with the fingers, and keeping the hand away from the back of the stopper.
- Keep the index finger of the drilling hand against the barrel of the borer and close to the stopper to stop the borer when it breaks through. Preferably, drill only part way through and then finish by drilling from the opposite side.
- Discard a stopper if a hole is irregular or does not fit the inserted tube snugly, if it is cracked, or if it leaks.
- Corks should have been previously softened by rolling and kneading. Rubber or cork stoppers should fit into a joint so that one-third to one–half of the stopper is inserted.
- When available, glassware with ground joints is preferable. Glass stoppers and joints should be clean, dry and lightly lubricated.
16.14.3 Insertion of Glass Tubes or Rods into Stoppers16.14.3 Insertion of Glass Tubes or Rods into Stoppers
The following practices will help prevent accidents:
- Make sure the diameter of the tube or rod is compatible with the diameter of the hose or stopper.
- If not already fire polished, fire polish the end of the glass to be inserted; let it cool.
- Lubricate the glass. Water may be sufficient, but glycerol is a better lubricant.
- Wear heavy gloves or wrap layers of cloth around the glass and protect the other hand by holding the hose or stopper with a layered cloth pad.
- Hold the glass not more than 5 cm from the end to be inserted.
- Insert the glass with a slight twisting motion, avoiding too much pressure and torque.
- When helpful, use a cork borer as a sleeve for insertion of glass tubes.
- If appropriate, substitute a piece of metal tubing for glass tubing.
- Remove stuck tubes by slitting the hose or stopper with a sharp knife.
16.14.4 Assembling Apparatus16.14.4 Assembling Apparatus
Following these recommendations will help make apparatus assembly easier and equipment safer:
- Keep your work space free of clutter.
- Set up clean, dry apparatus, firmly clamped and well back from the edge of the lab bench making adequate space between your apparatus and others work. Choose sizes that can properly accommodate the operation to be performed. As a rule, leave about 20% free space around your work.
- Use only equipment that is free from flaws such as cracks, chips, frayed wire, and obvious defects. Glassware can be examined in polarized light for strains. Even the smallest crack or chip can render glassware unusable. Cracked or chipped glassware should be repaired or discarded.
- A properly placed pan under a reaction vessel or container will act as secondary containment to confine spilled liquids in the event of glass breakage.
- When working with flammable gases or liquids, do not allow burners or other ignition sources in the vicinity. Use appropriate traps, condensers, or scrubbers to minimize release of material to the environment. If a hot plate is used, ensure the temperatures of all exposed surfaces are less than the autoignition temperature of the chemicals likely to be released and that the temperature control device and the stirring / ventilation motor (if present) do not spark.
- Whenever possible, use controlled electrical heaters or steam in place of gas burners.
- Addition and separatory funnels should be properly supported and oriented so that the stopcock will not be loosened by gravity. A retainer ring should be used on the stopcock plug. Glass stopcocks should be freshly lubricated. Teflon stopcocks should not be lubricated.
- Condensers should be properly supported with securely positioned clamps and the attached water hoses secured with wire or clamps.
- Stirrer motors and vessels should be secured to maintain proper alignment. Magnetic stirring is preferable. Only non-sparking motors should be used in chemical laboratories. Air motors may be an option.
- Apparatus attached to a ring stand should be positioned so that the center of gravity of the system is over the base and not to one side. There should be adequate provision for removing burners or baths quickly. Standards bearing heavy loads should be firmly attached to the bench top. Equipment racks should be securely anchored at the top and bottom.
- Apparatus, equipment, or chemical bottles should not be placed on the floor. If necessary, keep these items under tables and out of aisleways to prevent creating a tripping hazard.
- Never heat a closed container. Provide a vent as part of the apparatus for chemicals that are to be heated. Prior to heating a liquid, place boiling stones in unstirred vessels (except test tubes). If a burner is used, distribute the heat with a ceramic-centered wire gauze. Use the thermometer with its bulb in the boiling liquid if there is the possibility of a dangerous exothermic decomposition as in some distillations. This will provide a warning and may allow time to remove the heat and apply external cooling. The setup should allow for fast removal of heat.
- Whenever hazardous gases or fumes are likely to be evolved, an appropriate gas trap should be used and the operation confined to a fume hood.
- Fume hoods are recommended for all operations in which toxic or flammable vapors are evolved as is the case with many distillations. Most vapors have a density greater than air and will settle on a bench top or floor where they may diffuse to a distant burner or ignition source. These vapors will roll out over astonishingly long distances and, if flammable, an ignition can cause a flash back to the source of vapors. Once diluted with significant amounts of air, vapors move in air essentially as air itself.
- Use a hood when working with a system under reduced pressure (which may implode). Close the sash to provide a shield. If a hood is not available, use a standing shield. Shields that can be knocked over must be stabilized with weights or fasteners. Standing shields are preferably secured near the top. Proper eye and face protection must be worn even when using safety shields or fume hoods.
16.14.5 Mercury Containing Equipment16.14.5 Mercury Containing Equipment
Elemental Mercury (Hg) or liquid Mercury is commonly seen in thermometers, barometers, diffusion pumps, sphygmomanometers, thermostats, high intensity microscope bulbs, fluorescent bulbs, UV lamps, batteries, Coulter Counter, boilers, ovens, welding machines, etc.
Most of these items can be substituted with equipment without Mercury, thus greatly decreasing the hazard potential. Larger laboratory equipment may be more difficult to identify as “Mercury containing” due to the fact that mercury can be hidden inside inner components such as switches or gauges.
The concerns surrounding mercury containing equipment are:
- It is difficult to identify exposures or cross-contamination due to Mercury leaks or spills.
- The amount of Mercury used is usually much greater than the Department of Environmental Conservation (DEC) reportable quantities for releases to the environment.
- People may be unaware of the Mercury and thus may not be properly trained for use, maintenance, spills, transport or disposal or may not use the appropriate engineering controls or Personal Protective Equipment (PPE).
- There is legal liability if human health and the environment are not properly protected.
To minimize the potential for Mercury spills and possible exposures, laboratory personnel is strongly encouraged to follow these recommendations:
- Identify and label “Mercury Containing Equipment”.
- Write a Standard Operating Procedure (SOP).
- Train personnel on proper use, maintenance, transport and disposal.
- Conduct periodic inspections of equipment to ensure no leaks or spills have occurred.
- Consider replacing Mercury with electronic or other replacement components.
- Have available proper PPE such as nitrile gloves.
- Use secondary containment, such as trays as a precaution for spills.
- Plan for emergency such as a spill or release of mercury.
- Decontaminate and remove Mercury before long-term storage, transport or disposal.
- For new equipment purchases, please attempt to procure instruments with no or little Mercury
16.15 Ergonomics16.15 Ergonomics
Many lab tasks such as looking through microscopes, working in exhaust hoods, pipetting, and continuously looking down for bench tasks require both significant repetitive movements and sustained awkward posturing. Often there is no leg room when sitting at counters or hoods, which causes more leaning and reaching. Although the essential job tasks probably cannot change, you can develop important personal strategies that can improve comfort and health. There may also be equipment changes you can make.
The section below outlines some steps you can take to reduce your risk for injury from this demanding work. Links to product ideas and additional related information are provided. Product links do not imply endorsement. Consider a free ergonomic evaluation of your specific environment (Cornell Musculoskeletal Injury Prevention Program)—additional information below) before purchasing equipment.
- Take the time to adjust the seat depth and chair back height and tilt in order to maximize individual back support. Consider a slightly reclined position to promote better support.
- Try using chairs “backward”, supporting the torso when leaning forward to do bench/hood/microscope work, as a means for changing positions throughout the day.
- Make sure the feet reach the floor, foot ring or separate footrest comfortably. The stabilization of both feet makes it easier to sit back in a supported manner. Some lab chairs have adjustable foot rings—consider this feature when buying new chairs. For lower surfaces use office-style footrests. NeXtep are adjustable rests that attach to the cylinder of lab stools. Another style of freestanding rest with extended height adjustment is by Safco or similar.
- Seat height—be sure lab chairs have adequate height adjustment. Extended cylinder heights (32 inch) may provide additional adjustment that will help employees comfortably reach/perform work at counter height.
- Pull your torso close to the work surface and then sit back. This technique will help avoid ‘perching’ on the edge of the chair.
- Select benches where there is leg room under the surface.
Standing all day for bench work, particularly on concrete/tile flooring, is difficult. The body requires time to recover from these demands, even within a given shift.Recommendations to minimize risks from extended standing include:
- Microbreaks--allow time (as little as 30 seconds - 1 minute every 20 minute) and a chair/stool so spinal structures and joints can recover from extended standing.
- Consider anti-fatigue matting in areas where practical.
- Proper footwear is important and using a foam/gel insole can also reduce fatigue. Remember, they need to be replaced before they appear worn out.
- Provide a footrest so you can elevate one foot, then the other. This will reduce static fatigue. If safe/appropriate, try opening cabinets to create a footrest.
- Be cognizant of neutral postures while working. Adjust the chair or microscope as needed to maintain an upright head position. Elevate, tilt or move the microscope closer to the edge of the counter to avoid bending your neck.
- Avoid leaning on the hard edges on the table - consider padding the front lip of microscope table (AliEdge or similar) or using forearm pads. A simple, versatile solution is a variety of foam pads, like Wedge-Ease. Be sure these supports do not cause awkward wrist postures when focusing/adjusting the stage.
- Keep scopes repaired and clean.
- Spread microscope work throughout the day and between several people, if possible.
- Observe seating adjustment and support techniques.
Additional resources can be found at Nikon Microscopy U and UC Berkeley.
Below are some general guidelines to reduce the physical impact of pipetting.
- Sit or stand close to your work at bench. If safe/appropriate, try opening cabinets to create legroom.
- Work at appropriate heights to minimize twisting of the neck and torso. Elevate your chair rather than reaching up to pipette.
- Alternate or use both hands to pipette.
- Select a lightweight pipette sized for your hand. Hold the pipette with a relaxed grip and use minimal pressure while pipetting.
- Avoid standing or sitting for long periods. Alternating between sitting and standing provides relief and recovery time for fatigued body structures. Additional resources can be found at UCLA, UC Berkeley
- Observe seating recommendations to promote supported postures.
- Position work supplies as close as possible in order to avoid awkward leaning/reaching while working. Consider turntables to rotate materials closer to the user. Be sure that only essential materials are in the hood to avoid unnecessary reaching around clutter.
- Consider lower-profile sample holders, solution container, waste receptacles to prevent awkward bending of wrist, neck and shoulders. Reduced repetitive movement also means increased efficiency.
Additional resources can be found at UCLA.
- Gloves — Wear slightly snug gloves to reduce forces on hands and improve accuracy during fine manipulation. Wearing loose gloves during pipetting and other tasks makes manipulating small materials more forceful and difficult.
- Rotate tasks throughout the work day and among several people, whenever possible. Take frequent small rest breaks (1-2 minute in duration) every 20 minutes. Every 45-60 minutes, get up to stretch and move.
- Take vision breaks during intensive computer and fine visual work. Every 20 minutes, close the eyes or focus on something in the distance.
Cornell Musculoskeletal Injury Prevention Program (MIPP). The MIPP provides ergonomics assessment, training and planning services to the Cornell Community. All Cornell employees are eligible for services with the approval of their supervisor or Human Resources representative. Benefit Services demonstrates its commitment to employee health by offering the MIPP at no charge to Cornell employees and departments. Remember, you do not have to be uncomfortable or injured to benefit from MIPP services. Ergonomics is most effective when services are utilized for prevention. For more information, contact the Lead Ergonomics Consultant at Cornell Musculoskeletal Injury Prevention Program.
Early treatment of discomfort/injury and the continuous development a healthier lifestyle are critical to remaining healthy and productive at work. Take advantage these valuable resources: Cornell Physical Therapy and Cornell Wellness.