This blast valve is designed and tested to protect an underground shelter from a 50 pound per square inch detonation.
In order to withstand this incredible pressure, this item is fabricated from 3/8" (.375 inch) steel. It is a heavy, robust item designed to keep the massive pressures of a nearby conventional or nuclear blast from injuring or killing the occupants of your bomb shelter.
The ARS-50-BV Automatic Double Acting Blast Valve automatically closes when the initial positive pressure wave from an explosion hits and automatically closes a second time (in the other direction) when the outside air pressure goes negative in relationship to the internal shelter pressure. When the outside air pressure returns to normal, the blast valve automatically returns to its normally open state. In other words, it lets air flow into your Safe Cell or out of your exhaust port for normal operation, but will not allow a blast of high-pressure air to enter your shelter - and bring contaminants with it.