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Security for Air Intakes
Providing Security for HVAC Air Intakes and Intake
Air
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| Air Intakes like the one circled above, should
be evaluated to ensure that no contaminants from discharge stacks
are entrained. |
The surge in concern for intentional contamination of workplaces with
biological and chemical agents can be addressed by protective measures
which also protect against routine and already present hazards presented
by normal conditions. Appropriate design of Heating, Ventilation and
Air Conditioning (HVAC) Systems will reduce the risk and the consequences
of intentional contamination as well as protect workers from routinely
observed problems with entrainment and re-entrainment of chemicals.
For example, re-entrainment of paint booth and paint oven emissions,
or combustion exhaust gases, has been a recurring problem in UAW-represented
facilities. The following ideas were contributed by Jeff Burton, a well-known
ventilation consultant who provides training in this area. Local union
representatives should review the ventilation systems of their facilities
in light of these ideas. Should their installation fall short, we recommend
purchase of the training materials for a fuller understanding, and finding
a qualified professional to design the retrofit.
Potential intake contaminants and contaminators include:
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Odors, chemical gases and vapors, aerosols (example,
from nearby exhausts, stacks and vents).
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Odors and humid air (example, from kitchens).
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Mold spores, decay byproducts and their odors
(example, water infiltration and/or mold growing in the outside air
return, the air return mixing plenum and settled water near intake.)
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Automobile exhaust, this includes: CO, smoke,
volatile organic chemical (VOC) and diesel smoke, from parking garages,
nearby streets, loading areas, and so forth.
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Truck or engine exhaust from loading docks and
emergency generators.
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Tobacco smoke from smokers standing near an air
intake.
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Combustion byproducts from open fires and incinerators.
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Dust from streets, fields, ground care and wind-blown
settled materials.
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Herbicides, pesticides, rodenticides from grounds
keeping or building care.
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Biogenic materials (example, virus, bacteria,
pollen, mold spores, insect parts) from grounds care, evaporative
cooling towers, intentional human contamination (for example, pranksters,
mentally deranged, terrorist activity), and so forth.
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Any toxic chemical from adjacent industrial processes,
labs or effluent stacks.
To avoid HVAC system intake air contamination
(a partial list):
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Do not locate air intake at ground or below-ground
level.
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If located at ground level, plan to re-locate
intake or move intake opening to above ground level. American Society
of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE)
recommends a location on the lower one-third of the building wall
(assuming a tall building) but high enough to avoid wind-blown dust,
vehicle exhaust, tobacco smoking, grounds-keeping activities, and
intentional human contamination.
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Follow ASHRAE 62 and other proposed recommendations
(see page 12-10 of the IAQ and HVAC Workbook for a complete list)
for separation of intakes and potential contaminant sources (example,
15 to 25 feet from evaporative cooling towers).
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Find and remove, eliminate or minimize potential
intake contaminant sources.
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Install AMCA-certified louvers or grilles over
intakes (and include bird screens where applicable).
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Maintain HVAC filters and scrubbers in excellent
operating condition.
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Provide for MERV 10 or higher filtration in HVAC
systems. (This is not a trivial exercise.)
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Restrict tobacco smoking near intakes.
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Don't locate the intake within an architectural
screen if it also contains a contaminant source (example, exhaust
outlet, lab fume hood stack).
The following suggestions are intended to help avoid
intentional human-source contamination of HVAC systems and equipment:
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Include air intake security in existing and future
building security plans.
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Use fencing and screens to restrict unauthorized
access to air intake.
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If the intake is on roof, lock, secure or monitor
access doors and emergency access routes, stairs and ladders. (check
local fire codes).
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Provide surveillance of intake areas and nearby
grounds and roof (video cameras, monitors, dogs, guards).
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Install real-time air-contaminant monitors in
intake air.
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Interlock real-time air monitors and fan operation
to shut down system if contaminated with target chemical/biogenic
material.
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Consult with security experts.
Adapted from IAQ and HVAC Workbook, 4th Edition, 2001
More Information: D. Jeff Burton www.eburton.com
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