| Blast
valves are mounted over the air intake and air outflow pipes
inside a bomb shelter. As a high pressure wave from a nearby
detonation passes over the shelter, the pressure travels
down the pipes and into the shelter. If it is not stopped,
it will destroy the air filtration equipment and injure
or kill the occupants. Directly behind this high pressure
wave is a vacuum wave - the atmosphere is blown outward
from the center of the detonation. This vacuum wave can
be as deadly as the pressure wave. That is why these valves
are double acting - for both pressure and vacuum.
These
blast valves automatically and near
instantly 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 (a vacuum) 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 and 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.
In
order to withstand this pressure, these blast valves are
fabricated from ASTM grade A steel. This 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.
These
blast valves feature a lock down feature
that allows you to lock the valve in the closed position.
If you have a structural fire above your shelter or a malicious
person dumping water or smoke down your vent pipes, you
can remove the air intake hose or overpressure valve lock
the valve shut. See the manual
for more information.
Blast
valves are only necessary in hardened bomb shelters and
should be used in pairs - one on the air intake pipe and
one on the air outflow pipe. They install on the
inside wall of an underground blast resistant shelter right
over the air intake and outflow ventilation
pipes. Included are a heavy duty 1/4"
neoprene gasket, concrete wedge anchors, and a masonry bit
for the anchors.
The
air intake blast valve has the air intake hose from the
Safe
Cell slipped onto it, the air outflow blast valve has
the overpressure valve slipped onto it. The airflow is:
- Down
the intake ventilation pipe
- Through
the wall or ceiling
- Through
the blast valve
- Through
the air intake hose
- Through
the NBC filter bank
- Out
of the Safe Cell
- Throughout
the shelter
- Through
the overpressure valve
- Through
the outflow blast valve
- Up
through the outflow vent pipe
True
ventilation requires air in and air out. You control where
the air enters and where it leaves - every bit of it being
filtered by the Safe Cell.
For
more information, please see the installation
and operation manual (PDF).
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