MIL-HDBK-1027/1B
b)
Purge air should flow at the full design rate.
3.11.3
Combustion Air. The exhaust system should deliver
sufficient air to allow complete combustion. In the case of
propane, it takes 23 parts of air for each part of fuel for
theoretical complete combustion. Device burners do not
provide any primary air therefore combustion air must be
provided by the facility ventilation. In addition, enough
excess air must be delivered to provide realistic flame
characteristics. When a fuel is burned in the open, the flame
induces into it approximately 10 times the air needed for
perfect combustion. The trainer should be capable of providing
this air to produce a natural looking fire. This excess air
should enter the compartment at low velocity and not be directed
at the flame.
3.11.4
Exhaust. The exhaust system should be designed to
conform to the following criteria:
a) Once inside the compartment, the air should be
heated, collected at the ceiling, ducted to a common point then
to the exhaust fans and then to the treatment if necessary. The
duct and fan layout should allow for the future addition of a
pollution control device. Every attempt should be made during
the design of the structure to ensure that air is collected and
leaves the structure through the exhaust system. Minimize
leaks. Roof entries provide another escape path for the
products of combustion and should be ducted into the exhaust
system through manual dampers.
b) Each training compartment should have a separate
duct to carry away the products of combustion.
c) The exhaust stack should be designed to have a
height of 1.4 to 2.0 times the training structure height, which
would eliminate short circuiting and contamination of fresh air
entering the trainer. The stack should be designed to meet the
American Conference of Governmental Industrial Hygienists
(ACGIH) 2080, Industrial Ventilation, A Manual of Recommended
Practice.
d) A low velocity area should be provided prior to
the exhaust fan inlet to allow the PKP particulate to settle
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