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Subchapter 7. General Industry Safety Orders
Group 18. Explosives and Pyrotechnics
Article 120. Mixing Blasting Agents

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§5342. Mixing Buildings.

(a) Buildings used for the mixing of blasting agents shall conform to the requirements of this section. Buildings constructed after May 21, 1971, shall be noncombustible construction or of sheet metal on wood studs.

(b) The layout of the mixing building shall provide physical separation between the finished product storage and the mixing and packaging operation in accordance with applicable intraline distances contained in Section 5327.

(c) Floors in the processing plant shall be of concrete or of nonabsorbent material and free of cracks and crevices.

(d) Floors shall be constructed to eliminate open floor drains and piping into which molten materials could flow and be confined in case of fire.

(e) Liquid fuel shall be stored outside the mix building and away from the oxidizer area. The storage area shall be designed and located in such a manner that in case of tank rupture, the oil fuel shall be retained or be drained away from the mixing plant building. The shut-off valves shall be at the tank. Suitable means shall be provided to prevent the flow of oil fuel to the mixer in case of fire. In gravity flow systems, an automatic spring-loaded shut-off valve with fusible link shall be installed.

(f) The building shall be well ventilated.

Note: The recommendation for ventilation as contained in SLP No. 1, Institute of Makers of Explosives, 1993 Edition, is evidence of good practice.

(g) Heat shall be provided exclusively from a unit outside of the building or electric heat at a safe distance from combustible material.

(h) Personnel limits shall be established, posted, and enforced while operations involving blasting agents are underway at the mix house.

(i) Blasting agents and fuels shall be removed from the mix house and the equipment or area completely washed down before major work, other than routine maintenance, or open flame repairs are made.

(j) Before welding or repairs to hollow shafts, all oxidizer material shall be removed from the outside and inside of the shaft and the shaft vented.

(k) All internal combustion engines used for electric power generation shall be located outside the mixing plant building at least 50 feet from any opening in the building or shall be properly ventilated and isolated by a fire wall having a minimum one hour fire-resistance rating. The exhaust system on all such engines shall be equipped with a spark arrestor and shall be located so any spark emission cannot be a hazard to any material in or adjacent to the plant.


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


1. Amendment filed 10-17-75; effective thirtieth day thereafter (Register 75, No. 42).

2. Amendment filed 7-16-76; effective thirtieth day thereafter (Register 76, No. 29).

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

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