OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.

April 16, 1976

Mr. Richard D. Green
Application & Development Manager
MAPP Products
P.O. Box 105
Springfield, New Jersey 07081

Dear Mr. Green:

This is in response to your letter of March 31, 1976, regarding a clarification of 29 CFR 1926.350 and 29 CFR 1926.800 as they apply to MAPP gas, trade name for methlacetylene-propadiene, stabilized (MPS).

The Occupational Safety and Health Administration's (OSHA) position is that methylacetylene-propadiene, stabilized, by definition, is not a liquefied petroleum gas, but is considered as a fuel gas.

Gasoline and liquefied petroleum gas are specifically prohibited for use in tunnels in 29 CFR 1926.800(e)(1)(v). Other than this restriction, fuel gases may be used. However, fuel gas containers (cylinders) may not be used or stored in confined spaces (29 CFR 1926.350(b)(4)). A confined space is defined in 29 CFR 1926.21(a)(6)(ii). There may or may not be a confined space in a tunnel, depending on the tunnel's physical characteristics.

MPS may be used for purposes such as cutting, welding, heating in relation to cutting and welding, and heat-treating operations in confined spaces or other spaces, including tunnels. When this fuel gas (MPS) is used, all applicable OSHA standards and the manufacturer's recommendations must be followed. It is noted for underground operations, that ventilation must be mechanically supplied in quantities and lineal movement sufficient to prevent accumulations of escaped gas above the level allowed in 29 CFR 1926.800(c).

In view of the above, if you feel a meeting would be beneficial, please contact me.


Donald A. Shay,
Director Office of Compliance Programming