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, ,