TM-5-855-4
(1) Leakage of underground structures is inexistent, and above-ground a gastight enclosure is
required to prevent air contaminants from infiltrating the facility under attack. Air lock scavenging
requirements (discussed in chapter 6) are proportional to the time allocated to personnel ingress. Fresh
air provisions for personnel support are to dilute body odors, tobacco smoke, cooking, and other products
due to occupancy.
(2) The American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc.
(ASHRAE) Standard 62 lists minimum and recommended ventilation rates for various residential,
commercial, industrial, and institutional structures. The normal allocation is 10 cubic feet per minute
(cfm) per person for nonsmoking areas and 15 cfm per person for smoking areas. The lower limit for
outside air ventilation is 5 cfm per person for maintaining proper carbon dioxide and oxygen levels.
b. In general it will be more effective to use an open ventilation system during the pre-attack time
frame. The design of this system is similar to the ventilation systems found in conventional facilities,
except that a hardened AES will be used to exchange air between the facility and the atmosphere. The AES
is discussed in TM 5-858-5. Transattack/post-attack ventilation systems that communicate with the
atmosphere must provide for the removal of insidious DB and other contaminants. This extremely
difficult task will be avoided by using a closed ventilation system whenever possible.
c. Mechanical ventilation of underground installations is a necessity because natural ventilation is
not practical for enclosed structures of facilities such as kitchens, dining areas, and lavatories. During
normal periods of operation, there will be no recirculation of air supplied to kitchens, lavatories, toilet
rooms, bathrooms, restrooms, and battery rooms. During seal-up, this air will be recirculated through
carbon filters for odor removal. Recirculation of battery room air is permissible if batter charging
operations are interrupted; otherwise hydrogen scrubbing will be provided. Air from decontamination
areas will not be recirculated unless first passed through CB filters.
d. The ASHRAE recommendations for kitchens is at least 8 air changes per hour, but no less than 4
cfm per square foot of floor area. The quantities exhausted through hoods over ranges and other cooking
devices will be sufficient to maintain a velocity of 60 to 75 feet per minute (fpm) through the projected area.
For lavatories, toilet rooms, bathrooms, locker room, and restrooms, at least 4 air changes per hour but no
less that 200 CFM, 7 cfm per locker, 25 cfm per water closet or urinal, 50 cfm per showerhead, or 2 cfm per
square foot of floor area, whichever is greater.
e. Air supplied to offices and workrooms and exhausted via corridors will be used to ventilate toilets.
For battery rooms, at least 1 cfm per charging ampere will be provided, but no less than 6 air changes per
hour. Specific system applications covered in TM-5-810-1 are; administrative, community, storage, and
computer facilities; research and development laboratories; and mechanical rooms.
2-3. Combustion air.
a. The proper quantities of outside air required for combustion processes are determined by the power
supply and heat generators. Design guidelines for power supply are covered in TM-5-858-7. The diesel
engine is the most likely prime mover for the power systems. Batteries and similar energy storage
systems, which are bulky and have limited capacity, are practical only for the smaller shelters.
Geothermal and nuclear-reactor-based power systems will only apply to the very largest facilities.
b. Space limitations and exorbitant combustion air requirements of coal and oil fired boiler plants
for power generation all but eliminate these from consideration, especially in underground installations
where combustion type boilers are excluded. For gasoline and diesel engine drives, air requirements per
kilowatt (kW) are in the 4 to 7 cfm per kW range. For gas turbine drives, the range is from 9 to 13 cfm per
kW.
c. Because outside air for personnel may be interrupted during the attack mode, combustion air for
power generation must come from the structure itself or from an air intake structure separate from the air
intake for personnel. Steam and hot water boilers may be used for heating and domestic hot water loads.
These loads are usually expressed in British thermal units per hour (Btuh). For boiler combustion air
estimating purposes, use 2.5 cfm per 10,000 Btuh. This combustion air requirement maybe combined with
the personnel outside air requirements.
d. If a facility with an air-breathing power plant must be totally hardened, and if power production is
required before, during, and after an attack, the air intake and exhaust equipment must remain
operational at all times. The combustion air system will then include provisions to moderate the air inlet
temperature and filter and scrub all dust and crater ejects from the prime mover combustion air.
--
(1) A typical installation would consist of a dry inertial dust separator to remove approximately 90
percent of dust particles 20 microns and larger, and a wet scrubber to remove 85 percent of dust particles 5
2-2
Previous Page
