MSHA - Code of Federal Regulations - 30 CFR 18.98
30 CFR § 18.98
Enclosures, joints, and fastenings; pressure testing.
(a) Cast or welded enclosures shall be designed to withstand a
minimum internal pressure of 150 pounds per square inch (gage). Castings
shall be free from blowholes.
(b) Pneumatic field testing of explosion-proof enclosures shall be
conducted by determining:
(1) Leak performance with a peak dynamic or static
pressure of 150 pounds per square inch (gage); or
(2) A pressure rise and rate of decay consistent with
unyielding components during a pressure-time history as derived from a series
(c) Welded joints forming an enclosure shall have continuous gastight