Compressed Gas: Classification and Requirements

NFPA 55:3.3.49.1 Compressed Gas definition:

A material, or mixture of materials, that (1) is a gas at 68°F (20°C) or less at an absolute pressure of 14.7 psi (101.3 kPa) and (2) has a boiling point of 68°F (20°C) or less at an absolute pressure of 14.7 psi (101.3 kPa) and that is liquefied, nonliquefied, or in solution, except those gases that have no other health or physical hazard properties are not considered to be compressed gases until the pressure in the packaging exceeds an absolute pressure of 40.6 psi (280 kPa) at 68°F (20°C).

UC San Diego researchers working with compressed gases must follow an approved Hazard Control Plan (HCP) in using the HCP application

This HCP must be pre-approved by the principal investigator prior to beginning any work with this material.

Information on this Blink page is supplementary and is not intended to replace the approved HCP.

Use and storage of compressed gases is strictly regulated according to hazard classification.

• See the Toxic and Hazardous Gas Classifications Chart to identify the hazard class of a particular gas.

Compressed gases are classified as class I, II, III, or IV in order of decreasing hazard.* Classes are based on the lethal concentration to 50% of test animals (rats) of each gas (LC50).

* Note: The California Fire Code uses a different classification system. For more information, contact EH&S Fire & Life Safety, (858) 534-3659.

Storage and use requirements apply to all compressed gases.

• Read Compressed Gas: Storage & Handling for detailed information.

Implement additional safety precautions for strong>particularly hazardous substances (classes I, II, and III). Requirements are relaxed for small quantities and short term usage.

• See the Hazard Class Requirements Matrix for detailed information on requirements and exemptions.

• Follow the Chemical Hygiene Plan and Compressed Gas at all times.
• Complete your Compressed Gas and/or gas specific Hazard Control Plan (HCP) in the HCP application prior to ordering your material.
• There are fire code restrictions on the quantities of some gases regarding use and/or storage within research buildings. Examples include:
  • flammable (hydrogen, methane, acetylene)
  • oxidizer (oxygen, nitrous oxide)
  • highly toxic (arsine, phosphine, nitric oxide, nitrogen dioxide)
  • toxic (ammonia, hydrogen sulfide, carbon monoxide)
  • corrosive (hydrogen chloride, chlorine, hydrogen fluoride)
  • Unstable reactive (acetylene)
• Order only what is needed for a reasonable amount of time.
• Keep quantities to a minimum for all gases.
• Reduce concentrations when possible.
• Read Compressed Gas Cylinders Overview for details on ordering, services, and rental fees to complete your purchase.
• Order all in-stock and specialty gases through Marketplace.

This 2-video set was presented by Eugene Y. Ngai of Chemically Speaking LLC in May 2013 for UCSD researchers and Environment, Health & Safety staff. Key elements of a CG safety program and pre-planning for emergency response are covered.

• Video 1: Overview of Compressed Gas Safety (59:18 min.)
• Video 2:More on Compressed Gas Safety at UCSD (51:16 min.) with audience-driven topics

Safety training handouts presented with this program are below:

All files courtesy of Chemically Speaking LLC

• Compressed Gas Safety (PDF)
• Oxygen System Safety (PDF)
• Emergency Response:
  • Equipment (PDF)
  • Leak Detection (PDF)
  • Planning (PDF)
  • PPE and Decontamination (PDF)
• Silane Gas:
  • Silane Safety Notes (PDF)
  • Silane Incident Notes (PDF)

Gas cylinders are not always ideal in a lab setting for transportation, storage, safety, or other practical reasons. Consider the alternatives below:

• Gas generation

  Gas is generated on demand. This may alleviate fire code limitations on the storage and use of these gases:

  • Oxygen
  • Hydrogen
  • Arsine
  • Fluorine
  • Methylsilane
  • Ozone

• Subatmospheric gas cylinders

  Gas will flow out of the cylinder only if a vacuum is drawn on the cylinder valve outlet. Four types of systems are available that operationally meet this criteria:

  1. Gas adsorbed on a solid
  2. Gas complexed with a liquid
  3. Mechanical
  4. Gas generator

UC San Diego requirements for engineering controls, protective equipment, storage, emergency response, warning systems, and employee training are based on:

• Semiconductor Equipment and Materials International (SEMI) Facility Standards and Safety Guidelines
• Santa Clara County Toxic Gas Ordinance
• Occupational Safety and Health Administration Section 5(a)(1) – General Duty Clause
• Occupational Exposure to Hazardous Chemicals in Laboratories (Laboratory Standard) California – Code of Regulations (CCR), Title 8, §5191
• 2010 California Fire Code
• National Fire Protection Association (NFPA) Standard 318 (Protection of Cleanrooms)
• NFPA 55:3.3.49.1