Compressed Gas Cylinders: Gases

Flammable gases will ignite at a low flashpoint. Examples include propane, acetylene, hydrogen, methane, and iso-butane. Precautions include:

• Do not use near ignition sources (except for protected fuel gases).
• Have a portable fire extinguisher readily available for fire emergencies.
• Do not use a flame to detect for leaks! A compatible leak-detection solution must be used.
• Use spark-proof tools when working with, or on, a flammable compressed gas cylinder or system.
• Post a sign stating "No Open Flames" on access doors to areas which use or store flammable gases.
• Manifold systems must be designed and constructed by competent personnel who are thoroughly familiar with the requirements for piping of flammable gases. Consultation with the gas supplier, EHSS Fire Safey, and/or Facilities before installing manifolds is required.
• Piping, tubing and fittings for hydrogen must be approved for hydrogen service. Cast iron pipe and fittings must not be used. Plastic tubing must not be used unless it is approved for hydrogen service.

Cryogenic liquids and their boil-off vapors rapidly freeze human tissue and cause embrittlement of many common materials, which may crack or fracture under stress. All cryogenic liquids produce large volumes of gas when they vaporize, and may create oxygen-deficient conditions. Examples include liquid oxygen, hydrogen, nitrogen, argon, helium, and liquid neon. Precautions include:

• Transfer operations of cryogenic liquids must be conducted slowly to minimize boiling and splashing. Use appropriate personal protective equipment when transferring cyrogenic liquids, including insulated gloves, goggles and a face shield.
• In the event of skin contact with a cryogenic liquid, do not rub the skin. Place the affected part in a warm water bath.
• Use only equipment, valves, and containers designed for the intended product, service, pressure, and temperature.
• Inspect the containers for loss of insulating vacuum. If the outside of the jacket on a container is cold or has frost spots, some vacuum has been lost. Empty the contents into another cryogenic container and remove the damaged unit from service. Repairs should only be made by the manufacturer of the container or an authorized service provider.
• Excessive ice build-up (especially beneath the vaporizor or tank) could result in the discharge of excessively cold gas, or structural damage to the cryogenic container and surroundings.
• All cryogenic systems, including piping, must be equipped with pressure relief devices to prevent excessive pressure build-up.
• Do not use open flames or direct intense heat sources to thaw frozen equipment. Hot air, steam, or water can be used to thaw frozen equipment. Do not use water to thaw liquid helium equipment.

Oxidizing gases are non-flammable gases, but in the presence of an ignition source and fuel, can support and vigorously accelerate combustion. Examples include oxygen, chlorine, fluorine, and nitrous oxide. Precautions include:

• Do not use oil in any apparatus where oxygen will be used!
• Gauges and regulators for oxygen use should be labeled with a warning statement - "Oxygen - Use No Oil".

Inert gases are non-combustible, non-flammable, and non-reactive to many materials. Examples include argon, helium, nitrogen, and neon. Precautions include:

• Inert gases also displace oxygen and can produce a localized oxygen-deficient atmosphere, and therefore should not be used in enclosed or confined spaces without proper ventilation and/or respirator protection.
• Some inert gases are also cryogenic in their liquid state.
• Inert gases are odorless, colorless, and tasteless - making them even more dangerous because they cannot be detected by a person's senses. Always check for leaks and ensure equipment is in proper working order.

Toxic gases are those having a health hazard of 3 or 4, as defined by NFPA 704. The toxic effects of a substance can be either acute or chronic. Acute effects involve short-term, high concentrations that can cause irritation, illness, or death. Chronic effects involve continued exposure to a toxic substance over an extended period of time, resulting in serious and irreversible illness. Examples include arsine, phosphine, phosgene, and nitric oxide. Precautions include:

• Store all highly toxic gases in a continuously, mechanically ventilated gas cabinet, fume hood, or other enclosure (unless otherwise recommended by the supplier).
• Review the Material Safety Data Sheet (MSDS) to determine safe use guidelines.

Corrosive gases react to other materials and produce a chemical reaction which eats into, or gradually wears away the material. Corrosives can be hazardous to all parts of the body, and the eyes and respiratory tract are especially sensitive to exposure. Example include hydrogen chloride, chlorine, fluorine, and hydrogen fluoride. Precautions include:

• Check equipment and lines frequently for leaks. Metals can become brittle when used in a corrosive gas service.
• Use a diaphragm gauge with on equipment since steel or bronze gauges can be destroyed by corrosive gases. Check with the supplier for more information.
• Remove regulators after use and flush with dry air or nitrogen.
• Wear appropriate personal protective equipment, such as safety glasses or goggles, face shields, chemical-protective gloves, and aprons.