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Subchapter 7. General Industry Safety Orders
Group 18. Explosives and Pyrotechnics
Article 113. Explosives and Pyrotechnics

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§5244. Explosives for Underground Use.

(a) Tests made to determine the fume class as shown in the following table shall be made according to the standard for “toxic gas test” procedure of the Mine Safety and Health Administration (MSHA):

Cubic Feet of Toxic Gases Per

(1-1/4” X 8”) Cartridge of Explosive Material

Fume Class 1 -- Less than 0.16

Fume Class 2 -- From 0.16 to 0.33

Fume Class 3 -- From 0.33 to 0.67

(b) Except as provided for in subsections (c) and (d), main explosive charge used underground shall comply with the requirements for Fume Class 1.

(c) Where the concentration of combustible dust and vapor is found to exceed 10% of the lower flammable limit, loading and blasting operations with Fume Class 1 explosive materials shall be halted.

(d) When there is reason to believe that use of Fume Class 1 explosive materials may endanger employees by igniting combustible dusts or gases, permissible explosive materials shall be used and the ventilation increased to compensate for the resulting increase of poisonous and toxic gases.

Note: The composition of permissible explosives is such that they are less likely to ignite combustible dusts and gases than explosive materials which comply with Fume Class 1. On the other hand, the volume of poisonous and toxic gases produced by some permissible explosive materials is several times greater than that generated by Fume Class 1 explosive materials.

(e) Fume Class 1 explosives will not be required for the final loading of a coyote hole when the coyote hole is sufficiently back-filled to become a primary blast.

(f) Only plant mixed blasting agents where composition control is assured shall be used underground.


Authority cited: Section 142.3, Labor Code. Reference: Section 142.3, Labor Code.


1. Amendment of section and new Note filed 7-11-2003; operative 8-10-2003 (Register 2003, No. 28).

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