Basic Documentation

Laboratory Ventilation Codes and Standards
Siemens Industry, Inc. 98
Topic Requirement(s) Commentary
Ventilation
Rates for
Animal
Rooms
(Continued)
In some situations, the use of such a broad guideline might overventilate a
macroenvironment containing few animals, thereby wasting energy, or underventilate
a microenvironment containing many animals, allowing heat, moisture, and pollutants
to accumulate.
Modern heating, ventilation, and air conditioning (HVAC) systems (e.g., variable air
volume, or VAV, systems) allow ventilation rates to be set in accordance with heat
load and other variables. These systems offer considerable advantages with respect
to flexibility and energy conservation, but should always provide a minimum amount
of air exchange, as recommended for general use laboratories.
Individually ventilated cages (IVCs) and other types of specialized primary
enclosures, that either directly ventilate the enclosure using filtered room air or are
ventilated independently of the room, can effectively address animals’ ventilation
requirements without the need to increase macroenvironmental ventilation. However,
cautions mentioned above regarding high-velocity air should be considered.
Nevertheless, the macroenvironment should be ventilated sufficiently to address heat
loads, particulates, odors, and waste gases released from primary enclosures.
If ventilated primary enclosures have adequate filtration to address contamination
risks, air exhausted from the microenvironment may be returned to the room in which
animals are housed, although it is generally preferable to exhaust these systems
directly into the building’s exhaust system to reduce heat load and
macroenvironmental contamination.
Static isolation caging (without forced ventilation), such as that used in some types of
rodent housing, restricts ventilation. To compensate, it may be necessary to adjust
husbandry practices, including sanitation and cage change frequency, selection of
contact bedding, placement of cages in a secondary enclosure, animal densities in
cages, and/or decrease in macroenvironmental relative humidity to improve the
microenvironment and heat dissipation.
The use of recycled air to ventilate animal rooms may save energy but entails risks.
Because many animal pathogens can be airborne or travel on fomites (e.g., dust),
exhaust air recycled into HVAC systems that serve multiple rooms presents a risk of
cross contamination. Recycling air from nonanimal use areas (e.g., some human
occupancy areas and food, bedding, and supply storage areas) may require less
intensive filtration or conditioning and pose less risk of infection. The risks in some
situations, however, might be too great to consider recycling (e.g., in the case of
nonhuman primates and biohazard areas). The exhaust air to be recycled should be
filtered, at minimum, with 85-95% ASHRAE efficient filters to remove airborne
particles before it is recycled. Depending on the air source, composition, and
proportion of recycled air used (e.g., ammonia and other gases emitted from
excrement in recirculating air from animal rooms), consideration should also be given
to filtering volatile substances.
(Continued on Next Page)