16.4 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.
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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.
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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.
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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.
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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.