How to Work Safely with Compressed Gas Cylinders

One of the most common hazards in laboratories is compressed gas cylinders. Compressed gas cylinders can expose laboratory personnel to both chemical and physical hazards due to their pressure, content, and weight. Compressed gases can be toxic, flammable, oxidizing, corrosive, or inert, and leakage of any of these gases can be hazardous.

Because the gases are under high pressure, released gas can rapidly spread into a work area and endanger lab personnel. The type of gas that is released will have different consequences—none of them good. Inert gases can quickly displace breathing air, creating an oxygen-deficient atmosphere. Toxic gases can create poisonous atmospheres, while flammable or reactive gases can result in fire and explosion. Exposure to corrosive gases may destroy skin and eye tissue.

In addition, there are hazards from the physical weight of the cylinder and the pressure of the gas contained within the cylinder. A cylinder falling over or mishandled could result in broken bones, sprains, strains, and bruises. Moreover, if there is a sudden high-pressure energy release (e.g., if the valve is broken off), the cylinder will become a deadly missile, propelled with significant momentum and traveling at high speed.

According to OSHA’s Laboratory Standard, a compressed gas¹is:

a gas or mixture of gases in a container having an absolute pressure exceeding 40 psi at 70°F (21.1°C), or
a gas or mixture of gases in a container having an absolute pressure exceeding 104 psi at 130°F (54.4°C) regardless of the pressure at 70°F (21.1°C), or
a liquid having a vapor pressure exceeding 40 psi at 100°F (37.8°C) as determined by the American Society for Testing and Materials, ASTM D-323-72

Following the guidelines below will help ensure a safe lab.

General safe handling of compressed gas cylinders

The safety process begins when a full compressed gas cylinder is delivered to a facility. Compressed gas cylinders must be handled with caution at all times to prevent accidents or damage to the cylinder. Only those familiar with the properties, proper uses, and safety precautions of the gases being used should handle compressed gas cylinders.

Compressed gases should only be used in adequately ventilated areas. Toxic, flammable, and corrosive gases should be handled carefully in a chemical fume hood. Cylinders should be used in rotation as received from the supplier.

Do’s:

Upon delivery, visually inspect compressed gas cylinders for external damage and ensure that all compressed gas cylinders bear labels that identify the contents
All damaged, leaking, or poorly maintained cylinders should be returned to the supplier
Refer to Safety Data Sheets and other safety literature concerning the hazards, safe handling, storage, and disposal procedures of compressed gas cylinders
Observe all applicable federal, state, and local regulations
Wear appropriate personal protective equipment for each task, as well as for emergencies
Appropriate respirators should be kept available for immediate use when working with toxic gases
Secure cylinders vertically when in storage, transit, or use
Position cylinders so that the cylinder valve is easily accessible at all times
Pressure regulators and gauges must be compatible with the cylinder valves
Before lines and equipment are used, be sure all connections are tight, and leak-check the system at its working pressure
When discharging gas into a liquid, a trap or suitable check valve should be used to prevent back-flow of liquid
To prevent leaks, close the cylinder valve when the cylinder is not in use
Perform regular maintenance of cylinders, valves, regulators, and other devices

Don’ts:

Do not purchase more compressed gas than necessary to minimize the fire and toxicity hazards
Never use cast iron piping for chlorine
Never use copper piping for acetylene
Never place acetylene cylinders on their side
Do not place cylinders where they might become part of an electric circuit
Never strike an arc on a cylinder
Never repair equipment under pressure
Do not force or fix any cylinder connection that is not working properly
Do not use the cylinder valve itself to control flow by adjusting the pressure
Never leave the valve open when the equipment is not in use
Do not smoke around any compressed gas cylinder
Never refill a cylinder or mix gases in a cylinder

Valves, regulators, and piping

Piping, tubing, valves, fittings, and related components must be designed and fabricated from materials that are compatible with the gas being used. They must be of adequate strength and durability to withstand the pressure to which they are subject.

Piping systems should be inspected regularly for leaks
Do not use wrenches or pliers to open the cylinder valve
Never open the cylinder valve unless the regulator is attached and completely closed
All gas lines leading from a compressed gas supply must be clearly labeled to identify the gas
Tygon and similar plastic tubing should not be used for any portion of a high-pressure system
Teflon tape must not be used on CGA connections, which are equipped with either a metal-to-metal seal or a seal that incorporates a gasket
Avoid bending copper tubing sharply
Threads should never be forced if they do not fit exactly
Keep valves, regulators, and fittings free of oil and grease since there is a risk of explosion when oxygen or oxidizing gases come into contact with many organic substances

Transporting compressed gas cylinders

Always use a properly designed cart or hand truck for transporting cylinders. Cylinders should be securely chained or strapped in an upright position with protective valve caps in place. Do not drag, roll, or slide cylinders. Avoid dropping them and prevent them from striking anything forcefully. Never lift cylinders by the protective cap.

Compressed gas cylinder storage

Compressed gas cylinders must be stored in a dry and adequately ventilated area, upright, with the valve closed and protective cap in place. Cylinders should be firmly secured at all times. Where gases of different types are stored, cylinders should be grouped by types of gas. Gases that may react with each other must be stored separately.

Do not store in direct sunlight or expose cylinders to temperatures above 125°F
When stored indoors, maintain at least 20 feet between cylinders containing flammable gases and cylinders containing oxidizing gases or by a non-combustible barrier at least 5 feet high with a fire-resistance rating of at least one-half hour
Store cylinders away from heavily traveled areas and emergency exits; do not block any elevator, staircase, or evacuation route
Do not expose cylinders to conditions that may cause corrosion
Outside storage should be above grade, in a protected area to prevent deterioration from rain, snow, ice, and the sun

Empty cylinders

When the cylinder is empty, close the valve, bleed the system, and remove the regulator. The valve cap must be replaced, and the cylinder marked or labeled as "EMPTY" or “MT”. The cylinder should be returned to the storage area for pickup by the supplier.

Full and empty cylinders should not be connected to the same manifold; reverse flow can occur when an empty cylinder is connected to a pressurized system
Compressed gas cylinders should never be emptied to a pressure lower than 25 psi (172 kPa) as suction and backflow can cause contamination of residual contents with air if the valve is left open
Handle empty cylinders as carefully as full ones
Do not store full and empty cylinders together so there is no chance of confusing them

Disposing of compressed gas cylinders

Many suppliers have procedures in place for returning gas cylinders or bottles. They can normally be taken back to where they were originally bought, or the supplier may offer a collection service. Compressed gas cylinders that are not empty are not to be disposed of as general waste or placed in recycling dumpsters, as they may explode if crushed. Contact a hazardous waste facility, recycling, or disposal facility to determine the requirements for their criteria to accept the cylinders.

Since disposal is expensive, do not purchase lecture bottles or cylinders that cannot be returned to the distributor or manufacturer. If not returnable, follow the manufacturer’s directions for disposal and refer to applicable state and local laws

Training and emergency procedures

All laboratory workers must be trained to ensure they know about the hazards and safety precautions of the compressed gases present in their work area. They must know the specific procedures the employer has implemented to protect them from exposure, such as engineering controls, appropriate work practices, emergency procedures, and personal protective equipment to be used [29 CFR 1910.1450(f)(4)].¹

Laboratory personnel should be able to safely respond to a gas release or other emergency and be able to evacuate personnel and call for emergency assistance. Employees should know the location of the fire alarm pull station, fire extinguishers, main panel box, exits, shower/eye wash, first aid kit, and emergency telephone numbers.

General regulatory information

Compressed gas cylinders are primarily regulated at the federal level by OSHA and require routine inspections to ensure that the cylinders are in a safe condition. The proper handling, storage, and use of all compressed gas cylinders must be in accordance with Compressed Gas Association (CGA) Pamphlet P-1-1965. In addition, CGA requires that all cylinders be equipped with pressure relief devices [29 CFR 1910.101(a)-(c)].²

References

55 FR 3327 (1990). Occupational Safety and Health Administration: Occupational Exposure to Hazardous Chemicals in Laboratories, final rule (Codified at 29 CFR 1910).
Occupational Safety and Health Administration. General Industry Standards (29 CFR Part 1910). Washington, D.C.