6: Compressed Gas Cylinders

Compressed gases can be toxic, flammable, oxidizing, corrosive, inert, or some combination of these hazards. In addition to the chemical hazards, the amount of energy resulting from the compression of the gas makes a compressed gas cylinder a potential rocket. Appropriate care in the handling and storage of compressed gas cylinders is essential. The following are six general recommendations.

1. Know and Understand Gas Properties: Know and understand the properties, uses, and safety precautions before using any gas or gas mixture. Consult Material Safety Data Sheets (MSDSs) for safety information on the gases that you will be using.
2. Check Equipment: Leak test lines and equipment before they are used. Lines and equipment should be designed and maintained to handle full cylinder pressure. Materials of construction should be compatible with the gases being used.
3. Develop Emergency Plans: Be aware of potential hazards and develop plans to cover all possible emergencies. Include information about the types of gases used on your laboratory’s Emergency Information Poster.
4. Provide Personal Protection: Wear suitable protective clothing, including gloves and face protection. Safety equipment, such as self-contained breathing apparatus and fire extinguishers, should be located near hazardous areas. Stay well informed of the potential hazards of the gases with which you are working.
5. Follow Regulations: Follow all federal, state, and local regulations pertaining to the storage and use of compressed gas cylinders. Compressed Gas Association (CGA) Pamphlet P-1 provides excellent guidance. Follow the National Fire Protection Association (NFPA) codes, especially for flammable products.
6. When in Doubt, Contact Environmental Health & Safety: If you are unfamiliar with the hazards associated with a particular gas or unsure of the correct handling and storage procedures, call Environmental Health & Safety at 8-5294.

Primary Hazards

The following is an overview of the primary hazards to be avoided when handling and storing compressed gases.

	Asphyxiation: Simple asphyxiation is the primary hazard associated with inert gases. Because inert gases are colorless and odorless, they can escape into the atmosphere undetected and quickly reduce the concentration of oxygen below the level necessary to support life. The use of oxygen monitoring equipment is strongly recommended for enclosed areas where inert gases are being used.
	Fire and Explosion: Fire and explosion are the primary hazards associated with flammable gases, oxygen, and other oxidizing gases. Flammable gases can be ignited by static electricity or by a heat source, such as a flame or a hot object. Oxygen and other oxidizing gases do not burn, but will support combustion of flammable materials. Increasing the concentration of an oxidizer accelerates the rate of combustion. Materials that are nonflammable under normal conditions may burn in an oxygen-enriched atmosphere.
	Chemical Burns: Corrosive gases can chemically attack various materials, including fire-resistant clothing. Some gases are not corrosive in their pure form, but can become extremely destructive if a small amount of moisture is added. Corrosive gases can cause rapid destruction of skin tissue.
	Chemical Poisoning: Chemical poisoning is the primary hazard of toxic gases. Even in very small concentrations, brief exposure to these gases can result in serious poisoning injuries. Symptoms of exposure may be delayed.
	High Pressure: All compressed gases are potentially hazardous because of the high pressure stored inside the cylinder. A sudden release of pressure can cause injuries by propelling a cylinder or whipping a line.
	Improper Handling of Cylinders: Compressed gas cylinders are heavy and awkward to handle. Improper handling of cylinders could result in sprains, strains, falls, bruises, and broken bones. Other hazards such as fire, explosion, chemical burns, poisoning, and cold burns could occur if gases accidentally escape from the cylinder due to mishandling.

Handling, Storage, and Use of Gases

Only persons familiar with the hazards should handle compressed gas cylinders. All cylinder movement should be done with a compressed gas cylinder cart. Always secure the cylinders when in storage or use. Wear safety glasses, work gloves, and appropriate work shoes when necessary.

Compressed gas cylinders should not be subjected to any mechanical shock that could cause damage to their valves or pressure relief devices. Cylinders should not be dropped, dragged, slid, or used as rollers for moving material or other equipment.

Cylinder caps perform two functions. First, they protect the valve on the top of the cylinder from damage if it is knocked over. Second, if gas is accidentally released through the valve, the cap will vent the gas out of both sides, minimizing the likelihood that the cylinder will topple. Cylinder caps should not be removed until the cylinder is secured in place and ready for use.

Cylinder Storage Precautions

Several precautions should be taken during storage of compressed gas cylinders. Full and empty cylinders should be stored separately. Cylinders should be stored upright and secured at all times. Oxidizers and flammable gases should be stored in areas separated by at least 20 feet or by a 5 foot noncombustible wall.

Cylinders should not be stored near radiators or other heat sources.

Things to Keep Away from Cylinders

Several precautions should be taken to prevent the release of high-pressure gases, fire, and explosion. Compressed gas cylinders should not be exposed to sparks, flames, or temperatures above 125°F. Cylinders should not be places where they could come into contact with any electrical apparatus or circuits.

Smoking and open flames should not be permitted in areas used for storage of oxygen or flammable gas cylinders. Never permit oil, grease, or other combustible substances to come into contact with oxygen or other oxidizing gas cylinders, valves, and systems.

Returning Cylinders

When returning an empty cylinder, close the valve before shipment, leaving 25 psig of residual pressure in the cylinder. Replace the valve cap and any valve outlet caps or plugs originally shipped with the cylinder. If repair is needed on a cylinder or its valve, be sure to mark it and return it to the supplier.

Lecture bottles should always be returned to the distributor or manufacturer promptly when no longer needed.

Handling of Leaking Cylinders

Most leaks occur at the valve in the top of the cylinder and may involve the valve threads, valve stem, valve outlet, or pressure relief devices. Personnel should not attempt to repair leaking cylinders.

Where action can be taken without serious exposure to workers, move the cylinder to an isolated, well-ventilated area (away from combustible materials if the cylinder contains a flammable or oxidizing gas) and contact Public Safety.

Whenever a large or uncontrollable leak occurs, evacuate the area and immediately contact Public Safety.

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