ETL 1110-3-490
13 May 98
(b) Roughing Filter. Continuously operated filter systems will have a roughing filter with an
average efficiency of 25 to 30 percent when tested in accordance with ASHRAE 52.1. The
roughing filter extends the life of the intermediate filter or prefilter and reduces its change
(c) Prefilter. The prefilter or intermediate filter will have an average efficiency of 80 to 85
percent when tested in accordance with ASHRAE 52.1. The prefilter extends the life of the HEPA
filter and reduces its change frequency.
(d) HEPA Filter. The HEPA filter frame and filter media will meet the construction, material,
testing, qualification, and documentation requirements of ASME N509, N510, and UL 586 and
will have a filter efficiency of 99.97 percent at 0.3 m diameter particle size when tested in
accordance with the MIL-STD-282 dioctyl phthalate (DOP) test method. The filter frames will
meet the requirements of ASME AG-1a, Section FC. The HEPA filter medium will meet the
requirements of MS MIL-F-51079D.
(e) Adsorption Filter. The adsorber charcoal media will be designed to adsorb aerosol with a
minimum residence time of 0.25 seconds and will meet the requirements of MIL-PRF-32016(EA).
Typically, for commercial filters, two stages are required to achieve the 0.25 second residence time
at an airflow rate of 1,700 m3/hr (1,000 cfm) to 2,125 m3/hr (1,250 cfm). One stage of filter
adsorption can be used for airflow rates from 850 m3/hr (500 cfm) to 1,060 m3/hr (625 cfm). For
military applications, ASZM TEDA carbon conforming to EA-C-1704 will be used. A sample of
the ASZM TEDA carbon will be provided by the filter manufacturer for testing at the U.S. Army
Edgewood Research, Development and Engineering Center (ERDEC) as stated in MIL-PRF-
32016(EA). Funding for ERDEC testing is provided by the user. Filter trays not contaminated by
chemical surety materials or by super toxic materials can be refilled by the manufacturer, but any
contaminated carbon must be disposed of by the owning activity in accordance with local, state,
and federal regulations. A license must be obtained from the U.S. Department of Commerce
before an adsorption filter containing ASZM TEDA carbon can be shipped outside the United
States.
b. HVAC Requirements. For both new and existing facilities, an engineering evaluation will be
made to ensure that the AHU heating and cooling coils and facility piping will not freeze at low
outdoor ambient conditions during CP operations. If necessary, mechanical equipment modifica-
tions will be made to existing facilities and increased equipment capacities provided for new
facilities. Class II and III facilities may require that the CP system have partial or full heating or
cooling capability. The HVAC system must be designed, located, operated, and maintained to
provide uncontaminated air to the TFA. These requirements depend on the facility mission
requirements and must be coordinated with the user.
B-7
Previous Page
