Compressed Gas Safety for Laboratories Discussion topics: Potential hazards Safety considerations regarding: Selecting/ Receiving gases Handling cylinders Use & Storage Research Experiments & Systems Emergency procedures Stanford University Environmental Health & Safety Occupational Health & Safety Program, 725-3209, lsteng@stanford.edu Stanford Fire Marshal’s Office 723-0609, jleung@stanford.edu Conmpressedgas.Rev.9-2000.ppt IH Report#: 98-080 / SUFMO #02-00

Additional Training Will Be Required This training provides information about safe handling, storage and general hazards of compressed gases. It does not provide specific detailed training necessary to safely install or use compressed gases. Prior to actual use of any compressed gases your supervisor will need to provide operation specific training in this area. If you don’t understand ask questions! If you forget ask questions! If it doesn’t seem right ask questions! We would rather answer questions than deal with a accident……

Regulations for Compressed Gas Use & Storage Compressed gas use & storage are regulated by different organizations. California Fire Code Occupational Safety & Health Administration (CalOSHA) Santa Clara County Environmental Health Department

Characteristics of Gases Gases are much lighter than liquids & solids. The molecules of a gas are always in motion. Escaped gases will eventually distribute themselves throughout the air in a room or other confined space. Some gases have odors, some do not. Most gases are invisible, some can be seen. All gases have some property that can be hazardous to you.

Types of Gases Non-liquefied Compressed Gases – Nitrogen, Argon, Helium, Oxygen, Hydrogen Liquefied Compressed Gases-Chlorine, Hydrogen chloride, Carbon Dioxide, Nitrous Oxide, Dichlorosilane, Hydrogen Bromide Compressed Gases in a Solution-Acetylene Cryogenic Liquefied Gases-Nitrogen, Argon, Helium, Oxygen, Hydrogen

Potential Hazards High Pressure Asphyxiation Flammability Explosion Toxicity Corrosion Oxidation Pyrophoric Cryogenic Physical hazards: - PRESSURE: Valve breakoff, regulator failure. BAD! Health hazards: - asphyxiation (by physiological effect or gas can just force out oxygen in the air) Min 19.5% O2 for normal body function - specific toxicity Chemical hazards: (reactivity) - flammable gases - explosion w/ reactives: oxygen+ oil other oxidizers (Cl2, F2, nitrous oxide, nitrogen trifluoride), acetylene w/ copper contact - pyrophorics (silane, phosphine, arsine, etc.) - corrosives: special metals for fittings Gas Info For research uses, you need to be knowledgeable of the specific gases you are working with. For reference info of hazards & safe use, a good source is the: - Gas Data Book, Matheson

Purchasing/ Receiving Gases REDUCE YOUR RISKS! Select the lowest concentration of hazardous gas that will allow you to perform your experiment. Purchase the smallest quantities to satisfy your research needs. Select only gases that are delivered in returnable containers When receiving gas cylinders: Check for leaks Visually inspect for damage Ensure valve cover and shipping cap are properly in place. Check that cylinder is properly labeled Consider Gas generators: If extremely hi volumes of a particular gas is used on a semi-permanent basis, this eqpt. can help eliminate risks assoc. with cylinder changeouts. Smaller containers to avoid long storage time of gas cylinders. You should only purchase enough to use in 2 months. Less items stored = less risk Use returnable containers to reduce waste. Minimize purchase of lecture bottles. Very costly to dispose of. Proper labeling: Do not accept cylinders that are not IDed by name. Cannot rely on color coding.

Cylinder Story Cylinders come in different sizes, shapes and colors TAKE NOTE: Height & diameter = high center of gravity = not stable Pressure = enough to cause deadly damage, unguided missile Thus, special precautions for handling, storage, and use Remember the gas supplier must label the cylinder with the contents Check the label before you accept, move or use the cylinder.

Safe Handling of Gas Cylinders Before handling, make sure that valve cap is secured Transport gas cylinders using only a suitable cart Always take the safest most direct route when transporting gas cylinders Never leave un-restrained cylinders un-attended

Safe Storage of Compressed Gas Cylinders Only store cylinders in authorized locations. Separation of incompatibles (check SU storage group information) Restricted access to compressed gas cylinder storage. Store away from main building access/ egress points Separation of incompatibles: - 20 feet or proper firewall (non-combustible partition)--contact SU Fire Marshall Restricted access to avoid tampering by unauthorized personnel Electrical circuit-- especially careful during arc welding

Safe Storage of Compressed Gases Attach valve cap when a gas cylinder is not in service Cylinders must be stored upright Metal restraints at 1/3 AND 2/3 height of cylinder Max of 2 gas cylinders per set of chains Store upright: - helps prevent damage to valve - for liquid-fuel gases, ensures vapor phase to be in contact w/ pressure relief valve- to allow safe pressure relief Bench clamps: As proven in the Loma Prieta earthquake in ‘89, these bench clamps perform very poorly as a means of securing. EXCEPTION: allowed if bolted to the benchtop w/ cylinder stand. Per SC County, any regulator not connected to a process must be removed from the cylinder, and cylinder capped. Cylinder bench clamps are NOT allowed

Safe Use of Compressed Gases DO NOT tamper with the stem and cylinder valves NEVER use damaged regulators, connectors, piping, etc. For cylinders in use, cylinder valves must have hand wheel attached Close cylinder valve whenever: work is finished cylinder is empty Label empty cylinders Ensure safe & proper exhaust for purging & pressure relief for toxic, flammable, or corrosive gases Visual inspection of cylinder/ eqpt: Ensure no substantial corrosion. If suspect, contact supplier or EH&S Fire Safety for evaluation. Replace parts if necessary. Attachment: General Inspection Checklist When calling supplier, provide: - nature of problem - cylinder’s serial # Valve closed when: - work finished to-- lower risk of regulator failure - cylinder empty to-- avoid contamination of cylinder

Additional Precautions Some gases require special permits and controls for use. These are toxic, corrosive, flammable and pyrophoric gases. Check with SU EH&S during the design of the experiment in order to understand the permitting and engineering control requirements. For these gases, refer to attached information for specific safety precautions OXIDIZERS: oxygen, nitrous oxide, Cl2, F2,Nitrogen trifluoride, etc. - prevent contact w/ oil, grease, or other combustibles CORROSIVES: Cl2, F2, HCl, HF, NH3, etc. - proper maintenance of valves, regulators, etc. impt. ACETYLENE: - Incompatibility w/ copper, silver, mercury - regulators specific for acetylene CRYOGENIC LIQUIDS: N2, He, O2, Ar, Ne, etc. - Extreme cold can freeze human tissue on contact - Piping must integrate pressure relief devices TOXIC GASES: Ammonia, Arsine, Cl2, F2,CO, Et0, ClO2, etc. - Tightly regulated use. Contact the EH&S Lab Health & Safety Program Mgr.

Research Experiments and Systems Label all gas lines Remember to check safety devices (check valves, flow restrictors, pressure gauges, regulators) Select proper construction materials Leak test system before start-up & at cylinder changes Check for proper exhaust ventilation for the lab and apparatus prior to opening gas cylinders - Flow restrictors: Restricted Flow Orifices (RFOs) - Check valves: To protect from over-pressure & to prevent backflow - If designing a piping system for flammables, oxidizers, or pyrophorics, avoid using low-melting point metals (copper, brass, etc.) as specified in the fire codes. Stainless is preferred by the Fire Marshall’s Office. Also can refer to the Matheson’s Gas Data Book.

Emergency Procedures Standard Operating Procedures (SOP) BE PREPARED! Bottom line….Not only are they a good idea, they are required! BE PREPARED! Know your emergency procedures Know your emergency contacts Know what to do “if” the unexpected happens REFER to attached sheet for general tips on compressed gas emergencies

For More Information EH&S Compressed Gas training Guide to Safe Handling of Compressed Gases, Matheson Handbook of Compressed Gases, Compressed Gas Association Gas Data Book, Matheson Occupational Health & Safety Program- EH&S Ling Sue Teng, 725-3209, lsteng@stanford.eud Stanford Fire Marshal’s Office- EH&S Joseph Leung, 723-0609, jleung@Stanford.EDU