Flammable Gases

Flammable compressed gasses are often used in research and academic settings. Their use and storage is outlined in several different fire and safety codes including NFPA 55, NFPA 45, and OSHA 1910. Engineering data on specific gases, storage, and piping recommendations can be obtained from the Compressed Gas Association. 

Flammable Gas Definition

A flammable Gas is any substance that exists in the gaseous state at normal atmospheric temperature and pressure and is capable of being ignited and burned when mixed with proper proportions of air or oxygen. Certain flammable gases may be mixed with inert gas to reduce their flammability or render them non flammable. The reference for a mixed gases鈥 flammability should be the manufacturers supplied Safety Data Sheet. This is very common with Hydrogen, and in general a nonflammable mixture of hydrogen may be less than 5.5% H2 in Nitrogen, less than 3.1% in Argon, or less than 4.97% in Helium, as indicated on the SDS. Other flammable gases such as Methane, Ethylene, and Carbon Monoxide may have similar mixture classifications. 

Flammable Gas Storage

Storage of compressed gases is limited by building type and control area. These interpretations must be made by EH&S Staff members, but in general are limited to between 3-6 cylinders per control area. Since there may be several labs using flammable gases per control area, please consult with EH&S if you plan on using or storing flammable gas.  

Special ventilation requirements such as NFPA 55 compliant gas rooms or exhausted enclosures may be required for:

  • Ultrapure Hydrogen
  • Toxic or highly toxic gases
  • Pyrophoric gases
  • Carbon Monoxide

All flammable gas storage and use areas must be designated as such by posting appropriate 鈥淔lammable Gas鈥 signs on all entrances. Potential ignition sources such as bunsen burners and electrical equipment must be eliminated from designated areas. Mixtures of flammable gases must be labeled with the constituents and their concentrations prominently near the top of the cylinder, around eye level. 


In addition to these specific storage requirements, all other normal gas storage requirements apply:

  • All cylinders must be stored upright.
  • All flammable cylinders must be separated from oxidizers by 20 feet or a 陆 hour rated fire wall.
  • Cylinders must be chained or tethered to a sturdy surface to prevent tipping.
  • Cylinders must have the valve cap covered when in storage or a regulator attached if in use.
  • Cylinder contents must appear prominently on the tank, preferably near the top near eye level.
  • Cylinders must be stored away from heat and flame

Special Requirements for Research Laboratories:

Laboratories are classified from Class A-D according to fire hazard, with A being a high fire hazard and D being a minimal fire hazard.  Most research wet labs are classified as A,B, or C. The quantity of compressed gases allowed in research labs is determined by NFPA 55 Table 6.3.1.1. Laboratory quantities may also be reduced depending on their level above or below grade, as determined by EH&S.  

Special Requirements for Instructional Labs: 

Instructional labs are classified as C or D lab units and thus the storage of all gases must be limited to 10% of those allowed in NFPA 55 Table 6.3.1.1. The maximum quantity of flammable or oxidizing gases stored in instructional labs shall not exceed 100 cubic feet at STP. Gases classified as highly toxic or toxic by NFPA 55 shall not be permitted. 

Piping and Tubing

Official engineering sources such as the Compressed Gas Association should be considered, but in general these rules should be followed: 

  • Use the appropriate regulator designed for the gas. The best option is to rent it from the distributor.
  • Compatible tubing or piping must be used as described by the manufacturer or the appropriate Compressed Gas Association pamphlet.
  • Leak testing should be performed after installation and any time major changes are done to the area near the tubing run.
  • Piping should be secured permanently to a wall or ceiling in intervals described by the manufacturer or distributor.
  • Point of use locations should be equipped with shutoff valves unless located within 6 feet of the cylinder.