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Subchapter 7. General Industry Safety Orders
Group 18. Explosives and Pyrotechnics
Article 119. Manufacture of Explosive Materials

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§5328. Operation--Buildings and Equipment.

(a) Operating buildings or rooms in which more than 50 pounds of explosive materials which mass detonate are present at any time shall be constructed with at least one wall and roof of explosion-relief type. The direction of the relief wall shall be so placed as to be of least hazard to employees in adjacent buildings.

(b) When explosion pressure relief venting is required, the venting area shall be calculated on one square foot for each 35 cubic feet of building or room area.

(c) Floors and work surfaces shall be constructed to facilitate cleaning and to preclude, to the extent possible, cracks and crevices in which explosive materials can lodge/accumulate.

(d) When it is desirable to heat or cool buildings in which explosives are manufactured or charges are prepared, this shall be by steam, water, or other indirect sources. No floor registers will be permitted.

(e) All electrical wiring and equipment shall be in accordance with the Electrical Safety Orders.

(f) Bonding and grounding means shall be provided to prevent accumulation of static charges.

(g) Hydraulic or pneumatic presses and hand jacks shall be provided with pressure-relief valves so arranged and set that the material being processed will not be subjected to pressure likely to cause it to explode. Dies and plugged press equipment shall not be cleared by striking blows that may detonate or start the material burning.

Exception: Where provisions have been made to contain or preclude a fire/detonation.

(h) Explosives dust shall not be exhausted to the atmosphere. Where vacuum dust collection systems are used, they shall be designed by a qualified person, installed and maintained commensurate with the hazards involved, incorporating the following requirements:

(1) Adequate filters shall be installed between the source vacuum and the point of pick-up to prevent explosive materials from entering the vacuum pump or exhauster.

(2) The explosive material dust collection system shall be designed to prevent pinch points threaded fittings exposed to the hazardous dust and sharp turns, dead ends, pockets, etc., in which explosive materials may lodge and accumulate outside the collecting chamber.

(3) The entire vacuum collection system shall be made electrically continuous and be grounded to a maximum resistance of 5 ohms.

(4) Chambers in which the dust is collected shall not be located in the operating area unless protective shields adequate for the maximum quantity of material in the collector are furnished for personnel protection.

(5) No more than two rooms shall be serviced by a common connection to a vacuum collection chamber. Where interconnections are used, means shall be employed to prevent propagation of an incident via the collection piping.

(6) When collecting sensitive explosive materials such as black powder, lead azide, etc., a “wet” collector which moistens the dust close to the point of intake and maintains the dust wet until removed for disposal shall be used. Wetting agents shall be compatible with the explosive materials.

(7) Explosive material dust shall be removed from the collection chamber as often as necessary to prevent overloading, but under no circumstances shall the material be left in the chamber overnight. The entire system shall be cleaned at a frequency that will eliminate hazardous concentrations of explosive material dust in pipes, tubing, and/or ducts.

(i) Squirrel cage blowers shall not be used for exhausting hazardous fumes, vapors, or gases. Only non-sparking fan blades shall be used for fans located within the ductwork and through which hazardous materials are exhausted. Motors shall be located outside the duct.

(j) Work stations for explosive materials shall be separated by distance, barrier, or other means, so fire/initiation in one station will not initiate explosive materials in the next work station. When necessary, each operator shall be protected by a protective shield located between the operator and the explosive device or explosive materials being processed. This shield shall be designed to safely withstand a blast from the maximum amount of explosive materials allowed behind it.

(k) A prototype of the shield to be used shall be tested and proven sufficient for the anticipated conditions prior to an operational model being placed in service.

(l) If the personnel protection wall for the required operation becomes so large that it is impractical, the operator shall perform the operations by remote control or be protected by a suitably constructed shelter designed with a safety factor of not less than 4 to withstand the overpressure from the maximum amount of explosive materials in process.


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


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

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