Corrosive Materials; Flammable Materials; Oxidizers; Moisture Reactive; Compressed Gases; Toxic and Poisonous Substances

Standard Operating Procedure No. 5

Compressed Gases

Scope:    Oxygen, Nitrogen, Helium, Carbon Dioxide, Argon, Ammonia , Acetylene, Propane, Chlorine, Bromine, Fluorine

Hazards: The halogen gases are highly toxic, corrosive, and considered to be oxidizers.  Halogen gases are capable of initiating combustion, sometimes violently, when contacted with a variety of substances.  They all react violently with water and inhalation of their fumes can be fatal.  Hydrogen, acetylene, and propane are extremely flammable.  Ammonia, in addition to being highly toxic, can be explosive if involved in a fire due to the release of hydrogen gas.  Acetylene is highly reactive.  Oxygen acts as an accelerator if involved in a fire.

All pressurized cylinders allow rapid release of the gas and present physical hazards from flying debris.  Introduction of contaminates (e.g. oil) into cylinder equipment such as valve regulators can cause explosion.  All gases, regardless of toxicity, can cause death by asphyxiation.

Storage: Keep only cylinders currently in use in the laboratory area.  Secure all cylinders to a sturdy object such as a bench or stand using a cylinder strap or chain.  Lecture bottles should be isolated and securely stored away from students.  Store only in areas of good ventilation and protect from direct sunlight, rain, snow, heat, fire, and electrical contact.  Never store of use cylinders in corridors, stairwells, or high traffic areas.  Ensure all cylinders are labeled.  If empty, ensure cylinders are labeled “MT” or “Empty”.

PPE: Safety Goggles, Face Shield (When Connecting); Instructor Lab-coat

Usage:   Always know the identity of the gas before use.  Contact Facilities Services for disposal of unlabeled cylinders.  Do not exceed the design pressure of the apparatus being used.  Carefully inspect fittings, regulators, and apparatus for damage before using.  Use only regulators, gauges, and connections with matching threads and which are designed to be used with the gas and cylinder(s) involved.  Ensure thread sealing material is compatible with gas being used (e.g. Teflon tape).  Never lubricate, modify, force, or tamper with a cylinder valve.  Only use tools approved for cylinder connections.  Use non-sparking tools for flammable gas connections and ensure flammable gas cylinders are properly grounded.  Do not modify or alter cylinders or their attachments.

Use cylinder and manifold systems only with their appropriate pressure regulators.

Use cylinders in well-ventilated areas only.  Corrosive, toxic and flammable gases should only be used inside of the laboratory hood.  Open cylinder valves slowly to prevent rupture of attached tubing.  Never use compressed gases to blow away dust or dirt.  Do not extinguish a flame involving a highly combustible gas until the source of the gas has been shut off.  Otherwise it can re-ignite, causing an explosion.  Always use a trap to prevent siphonage of liquid chemicals and check valve to prevent back-flow of gases into the cylinder.  Safety traps should have a volume of one and one-half times the total liquid volume in the experiment.  Never bleed a cylinder completely empty.  Always leave a residual pressure of approximately 25 psig to keep contaminants out.

After making connections, check system for leaks using a substance compatible with the cylinder gas.  Periodically check cylinder fittings for leaks.  Do not move or use leaking cylinders.  If a cylinder is found to be leaking, isolate area and contact Facilities Services immediately.  Close cylinder and bench valves when the cylinder or gas is not in use.  Do not rely on pressure regulator valve for complete closure.

Waste:   Return empty cylinders to original supplier.  Contact Facilities Services for disposal of gas cylinders that are unreturnable or leaking.  Do not move leaking cylinders as instantaneous release of pressure can occur.