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Compressed Gas Safety for Laboratories

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Presentation on theme: "Compressed Gas Safety for Laboratories"— Presentation transcript:

1 Compressed Gas Safety for Laboratories
Discussion topics: Potential hazards Safety considerations regarding: - Selecting/ Receiving gases - Handling cylinders - Storage - Use Research apparatus/ systems Proper emergency procedures Stanford University Environmental Health & Safety Occupational Health & Safety Program, x5-3209, Stanford Fire Marshal’s Office X3-0609, Conmpressedgas.Rev ppt IH Report#: / SUFMO #02-00

2 Health & Safety Regulations- Compressed Gas Cylinders (CGCs)
Safety regulations (Cal/OSHA 8 CCR , California Fire Code Article 74 & 80) cover: Labeling & Construction of CGCs Safe handling of CGCs Safe use of CGCs Safe storage of CGSs Cal/OSHA regulations online:

3 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.

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

5 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

6 Purchasing/ Receiving Gases
REDUCE YOUR RISKS! Select least hazardous gases that will work Purchase only necessary quantities Select gases w/ returnable containers When receiving gas cylinders: Check for leaks Visually inspect for damage Ensure valve cover and shipping cap is on Check for proper labeling 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.

7 Cylinder Story Cylinders come in different sizes, shapes and colors
Name DOT Hazard Class 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.

8 Safe Handling of CGCs Before handling, ensure valve cap is secured
Transport CGCs using a suitable cart Never rely on valve cap as a handhold Always take the safest route for transport Do not leave un-restrained cylinders un-attended

9 Safe Storage of Compressed Gas Cylinders
CGC storage area requirements: Protected from: external heat sources passing/ falling objects Well-ventilated Isolation from highly flammable materials (>20 ft) Separation of incompatibles (check SU storage group information) Restricted access to CGCs Away from main access/ egress points Avoid forming part of an electrical circuit with the CGC (Safe storage- cont’d.) 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

10 Safe Storage of Compressed Gases
Attach valve cap when CGC is not in service CGCs shall be held in a suitable rack or secured to other rigid structures Cylinders must be stored upright Metal restraints at 1/3 AND 2/3 height of cylinder Max of 2 CGCs per set of chains Cylinder bench clamps are NOT allowed 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.

11 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 Never use cylinders as rollers or supports 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

12 Safe Use CGCs-- Special Precautions
Some gases require special permits and controls for operation. Toxic, corrosive, flammable and pyrophoric gases are examples. Check with your P.I., safety representative or SU EH&S before ordering any of these materials. 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.

13 Research Apparatus/ Systems
CGCs shall be equipped with connections complying with ANSI B / CGA (Cylinder Valve Outlet & Inlet Connections) Label all gas lines Remember safety devices (check valves, flow restrictors) Pressure gauges Select proper construction materials Leak test system before start-up Ensure exhaust ventilation for the lab and apparatus is on and working normally prior to opening CGC’s - 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.

14 Emergency Procedures BE PREPARED!
Know your emergency shutdown procedures Know your emergency contacts Know what to do “if” the unexpected happens Guidance on standard and emergency procedures: SOP’s are not only good ideas they are required Laboratory supervisor or local safety coordinator SU Health & Safety Manual REFER to attached sheet for general tips on compressed gas emergencies

15 For More Information 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, , Stanford Fire Marshal’s Office- EH&S Joseph Leung, ,

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