Method and apparatus for prevention, suppression or mitigation of explosions in confined subterranean chambers

The present invention is directed toward a method for preventing, suppressing or mitigating explosions in a confined subterranean chamber, access opening, or entryway of an underground structure such as the manhole of sewers, service boxes, and mining tunnels. The method utilizes a flexible bladder filled with an inert gas or explosion suppressing agent, wherein the bladder is maintained in the chamber in an inflated condition and the volume of the inflated bladder occupies greater than 70% of the volume of the chamber to significantly reduce the amount of space in which an explosive fuel/air mixture may otherwise accumulate. The bladder is heat critical to disintegrate at a predetermined temperature and release a volume of the explosion suppressing agent or inert gas relative to the volume of the chamber which is sufficient to alter the ratio of the fuel/air mixture in the chamber to prevent, suppress or mitigate the explosive reaction. The inflated bladder also serves as a compressible plenum or pressure accumulator to retard ultimate pressure buildup such that the pressures caused by a limited explosion are not transferred to the chamber cover and interconnecting ducts of the subterranean enclosure.