Chapter 2 - Engineering Controls

Engineering controls are considered the first line of defense in the laboratory for the reduction or elimination of the potential exposure to hazardous chemicals. Examples of engineering controls used in laboratories at Cornell include dilution ventilation, local exhaust ventilation, chemical fume hoods, glove boxes and other containment enclosures, as well as ventilated storage cabinets.

The OSHA Laboratory Standard requires that "fume hoods and other protective equipment function properly and that specific measures are taken to ensure proper and adequate performance of such equipment." General laboratory room ventilation is not adequate to provide proper protection against bench top use of hazardous chemicals. Laboratory personnel need to consider available engineering controls to protect themselves against chemical exposures before beginning any new experiment(s) involving the use of hazardous chemicals.

The proper functioning and maintenance of fume hoods and other protective equipment used in the laboratory is the responsibility of a variety of service groups. Facilities Services and Engineering, Building Coordinators, EHS, and other groups service equipment such as fire extinguishers, emergency eyewash and showers, and mechanical ventilation. Periodic inspections and maintenance by these groups ensure proper functioning and adequate performance of these important pieces of protective equipment.

However, it is the responsibility of laboratory personnel to immediately report malfunctioning protective equipment, such as fume hoods, or mechanical problems to their Building Coordinator as soon as any malfunctions are discovered.

2.1 Chemical Fume Hoods

Fume hoods and other local exhaust capture devices are designed to contain the release of hazardous vapors, fumes, gases, and dusts. Use of hazardous chemicals on the open benchtop is strongly discouraged. A fume hood must be used when working with materials that present an inhalation hazard, when conducting new or unknown chemical reactions, or when operations may generate heat, flames, or pressurized reactions.

Safe and Effective Fume Hood Use

To achieve optimum containment, personal protection, and energy efficiency:

Verify proper hood operation before use. Check the airflow monitor or Magnehelic gauge if one is installed. If no monitor is present, verify airflow using the paper tell-tale (crepe paper strip) at the sash opening.
Do not use a hood that appears to be malfunctioning.
If the hood is not functioning properly, notify the building coordinator or Facilities and Campus Services (FCS) immediately. Post a “Do Not Use” sign on the hood until repairs are completed:
Do Not Use Sign (docx)
Work at least 6 inches inside the hood. Position equipment as far back as practical to maintain stable airflow and maximize containment.
Do not block the baffles or place equipment on the lower airfoil. Obstructions reduce airflow and compromise containment.
Keep the sash at the recommended operating height. Lower sashes improve containment and reduce energy use.
Close the sash completely whenever the hood is not in use.
Do not use fume hoods to evaporate hazardous waste. Evaporating hazardous waste is illegal under state and federal environmental regulations.
For particularly hazardous substances (select carcinogens, reproductive toxins, volatile toxics, sensitizers, or reactive compounds), use additional engineering controls such as condensers, traps, or scrubbers to prevent release to the environment.
Do not exhaust equipment such as vacuum pumps through the face of the hood. This disrupts airflow and prevents proper sash closure.
Maintain good housekeeping. Keep the work area clean and free of clutter, wipe down surfaces regularly, and promptly clean chemical spills.

Testing, Inspection, and Training

Annual fume hood performance testing is performed by Facilities and Campus Services (FCS) Controls, including face velocity measurement and airflow pattern checks.

EHS evaluates hood use and ventilation conditions during routine laboratory safety assessments and provides guidance on safe hood operation and laboratory ventilation practices.

EHS offers an online Fume Hood Safety training program and maintains additional guidance in the Safe Fume Hood Use Guide.

2.1.1 Heating Perchloric Acid

DO NOT use heated Perchloric acid in a regular fume hood. If heated Perchloric acid is used in a regular fume hood (without a wash down function), shock sensitive metallic perchlorate crystals can form inside the duct work, and could result in causing an explosion during maintenance work on the ventilation system. Use of heated Perchloric acid requires a special perchloric acid fume hood with a wash down function. If you suspect your fume hood has perchlorate contamination or would like more information on perchloric acid fume hoods, then contact askEHS.

Laboratory groups who use these hoods shall document standard procedures for the frequency and length of running the washdown system. In some cases, this may be with every use. This procedure shall also include how often a complete cleaning of the hood surfaces is required in order to ensure that dust and splatter on the inside of the hood, that may contain perchlorate salts, do not build up.

2.1.2 Fume Hood Inspection and Testing Program

Annual fume hood testing is performed by Facilities and Campus Services (FCS) to verify ongoing performance and compliance with applicable ventilation standards. After each annual inspection, an inspection sticker is affixed to the fume hood indicating the date of the most recent test. If a hood does not meet performance criteria, a warning tag or sign will be placed on the hood indicating that it should not be used until corrective actions are completed.

When a hood is identified as unacceptable, the building coordinator and responsible facilities personnel are notified. They coordinate repair efforts and communicate with affected laboratory groups regarding temporary use of alternate hoods, if needed.

For details on fume hood operation, annual testing, and user expectations, see the Laboratory Ventilation page. For questions or concerns, contact askEHS .

If your fume hood does not have an inspection sticker, or if the sticker indicates that more than one year has passed since the last inspection, please notify your building coordinator or FCS so that testing can be scheduled. Users may also contact EHS for questions related to hood safety or laboratory ventilation practices.

Annual fume hood performance testing conducted by FCS typically includes:

Measurement of average face velocity to verify compliance with ANSI/AIHA Z9.5;
A visual performance check referencing ASHRAE 110 qualitative indicators;
Verification of basic airflow conditions and general room pressurization;
A housekeeping and utilization review to identify obstructions, improper storage, or practices that may affect performance.

The Hood Housekeeping Score (HHS) is used to document the general condition and use of the hood, with higher scores indicating more significant concerns. The scoring system is:

Hood Housekeeping Score (HHS)	Reason for Concern
1	Hood hibernated (intentionally out of service)
2	Hood in use, organized, minimal clutter
3	Hood on but empty or being used for storage
4	Hood in use with significant clutter or competing activities
5	Hood in use with contamination concerns
6	Hood decommissioned or removed from service

2.1.3 Installation of New Fume Hoods

Installation of a new fume hood requires careful planning and a clear understanding of the existing building ventilation systems and capabilities. Improperly installed fume hoods or other capture devices can disrupt airflow conditions in the room and negatively impact the performance of other hoods and the building’s overall ventilation system.

All fume hoods and other local exhaust or capture devices must be planned and installed in consultation with Facilities and Campus Services (FCS) and Environment, Health and Safety (EHS). All new installations must comply with the Cornell Design & Construction Standards, including the commissioning and turnover requirements described in Standard 115000. Under this standard, fume hood commissioning—including “as-installed” ASHRAE 110 testing, turnover documentation, and establishing new assets in Maximo—is a project deliverable performed by the commissioning vendor and coordinated by the Project Manager.

After installation and turnover, fume hoods become part of the university’s ongoing inspection and performance testing program. EHS reviews hood performance during routine laboratory safety assessments, and FCS Controls conducts required annual performance testing.

EHS is available during planning and design phases to provide guidance regarding the selection, placement, and safety requirements for laminar flow clean benches, biosafety cabinets (BSCs), ductless fume hoods, and other containment or local exhaust devices. Field certification of BSCs must be performed by a qualified NSF/ANSI 49–accredited contractor as part of equipment installation and turnover, coordinated through the Project Manager.

2.1.4 Removal of Existing Fume Hoods

Any removal of fume hoods and capture devices requires prior consultation with your Building Coordinator, Facilities Services, and EHS. This is necessary to ensure building ventilation systems are not affected by removal of fume hoods and capture devices, and so utility services such as electrical lines, plumbing systems, and water and gas supply lines are properly disconnected. For more information about decommissioning of fume hoods, go to the Laboratory Ventilation page.

There is an additional concern for the presence of asbestos within the fume hood itself, and potentially in any pipe insulation associated with the ductwork and/or Mercury in cup sinks. Any asbestos must be properly removed and disposed of by a certified asbestos removal company. EHS can assist laboratories with the cleanup of any Mercury contamination. Contact EHS at 607-255-8200 for more information or questions about potential asbestos or Mercury contamination. See the Lab Move Guide in the appendix for more information.

2.1.5 Maintenance Procedures For Fume Hoods

Please see the Laboratory Ventilation page for reference and training material.

2.2 Other Capture Devices

Engineering controls beside the fume hood include compressed gas cabinets, vented storage cabinets and local exhaust ventilation (LEV) such as capture hoods (canopy and slot), and snorkels. These work to capture and entrain chemical vapors, fumes and dusts at the point of generation. Examples where these devices would be appropriate are welding operations, atomic absorption units, vacuum pumps, work with dry nanomaterials and many other operations in the laboratory. Installation of any of these must be in the consultation of EHS and may include an engineering design to ensure the proper connection into the ventilation systems ductwork.

2.3 Glove Boxes

Glove boxes are sealed enclosures that are designed to protect the user, the process or both, by providing total isolation of the contents from the outside environment. They are usually equipped with at least one pair of gloves attached to the enclosure. The user manipulates the materials inside using the gloves. Typically, a glove box has an antechamber that is used to take materials in and out of the box.Types of Glove boxes:

Controlled Environment (dry box) - These create oxygen and moisture free conditions by replacing the air within the box with an inert gas, such as nitrogen, argon or helium, depending on the type of materials to be worked with. A "rotary vane vacuum pump" is used to remove the atmosphere. Additional accessories may be used, such a gas purifier, to further reduce oxygen and moisture levels for particularly sensitive operations. There are 4 types of this type of glove box based on their leak tightness. Class 1 having the lowest hourly leak rate. This should be inspected by a service company during commissioning, when the gloves are changed, or when there appears to be a problem with the functioning of the glove box.
Ventilated Glove box (filtered glove box) - These have filters, either HEPA or ultra low particulate, on the inlet and outlet ends of the box and a blower to circulate the air. These provide protection to the user through this filtration and also if the exhaust is connected to building exhaust through a thimble connection. These can have serve in cleanroom applications by reversing the airflow in the chamber to positive pressure.

Regular maintenance and inspection is essential to ensure that a glove box is adequately protecting the user, the environment and/or the product/process. Routine maintenance procedures and the frequency of inspection (or certification) should follow the manufacturers and regulatory recommendations.

There are various tests that can be performed on glove boxes, the suitability of which depends on the glove box and the application. Tests may include pressure decay (for positive pressure), rate of rise (for negative pressure), oxygen analysis, containment integrity, ventilation flow characterization, and cleanliness. The source of a leak can be identified using a Mass Spectrometer Leak Detector, ultrasound, the soap bubble method or use of an oxygen analyzer. For an in-depth discussion of glove boxes and testing, see: AGS (American Glove Box Society) 2007 Guide for gloveboxes – Third Edition. AGS-G001-2007.

Please see other references at the bottom of this page for further details.

2.4 Water Protection in Labs

Laboratory personnel must ensure that any piece of equipment or laboratory apparatus connected to the water supply utilizes backflow protection or is connected to a faucet with a vacuum breaker. The purpose of backflow prevention and vacuum breakers is to prevent water used in an experimental process or with a piece of equipment from back flowing and contaminating the laboratory’s and building’s water supply system. Examples of situations that can result from improper backflow protection include chemical contamination and/or temperature extremes (i.e. hot water coming from a drinking water fountain).