MIL-HDBK-1003/3
their life. Use the least efficient filter that will satisfy
mission requirements. Some available filter types and their
applications include the following:
Filter Type
Applications
Flat throwaway
Window air conditioners, warm air
furnaces, packaged unitary equipment,
central air handlers (when high
efficiency is not required)
Flat permanent
Same as for flat throwaway but require
cleaning
Roughing or pre-filters
For removing larger particles ahead of
high efficiency filters to extend
filter life
High efficiency air
Operating rooms, clean rooms,
(HEPA) filters
protective shelters
Renewable media
Large outdoor air systems with high
(auto-cleaning)
dust loads to reduce frequency of
filter changes; roughing or pre-filters
Electrostatic
For high efficiency with low pressure
drop (precede with pre-filter to reduce
cleaning requirements)
Consider also the ambient dust level of the air.
A classic illustration of poor design is a building at
a desert station with low air intakes located adjacent to an
unlandscaped helipad. Each time a helicopter lands or takes off,
huge quantities of dust are drawn into the HVAC filters. When
selecting a filter bank for an installation, consider the type of
fan and the fan curve. A packaged cabinet fan unit with forward
curved blades may not have sufficient static pressure to maintain
required airflow with dirty HEPA filters.
6.7
Access for Inspection and Maintenance. Air
distribution systems of an HVAC plant require access for
inspection and maintenance. During design consider how filters,
motors, and fan belts will be replaced and cleaned. Design
systems to avoid the following:
a) Using a step ladder in the middle of an office to
remove a ceiling tile and rig portable lighting to maintain
equipment.
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