29 CFR § 1926.904 - Storage of explosives and blasting agents.
(a) Explosives and related materials shall be stored in approved facilities required under the applicable provisions of the Bureau of Alcohol, Tobacco and Firearms regulations contained in 27 CFR part 55, Commerce in Explosives.
(b) Blasting caps, electric blasting caps, detonating primers, and primed cartridges shall not be stored in the same magazine with other explosives or blasting agents.
(c) Smoking and open flames shall not be permitted within 50 feet of explosives and detonator storage magazine.
(d) No explosives or blasting agents shall be permanently stored in any underground operation until the operation has been developed to the point where at least two modes of exit have been provided.
(e) Permanent underground storage magazines shall be at least 300 feet from any shaft, adit, or active underground working area.
(f) Permanent underground magazines containing detonators shall not be located closer than 50 feet to any magazine containing other explosives or blasting agents.