Basic Documentation

Laboratory Ventilation Codes and Standards
Siemens Industry, Inc. 146
Topic Requirement(s) Commentary
Recirculated
Air and Cross
Contamination
(Continued)
Institute of Laboratory Animal Research, Commission on Life Sciences,
National Research Council, Guide for the Care and Use of Laboratory Animals,
Eight Edition, 2011:
Page 46: The use of recycled air to ventilate animal rooms saves considerable
amounts of energy but might entail some risk. Many animal pathogens can be
airborne or travel on fomites, such as dust, so exhaust air to be recycled into
heating, ventilation, and air-conditioning systems that serve multiple rooms presents
a risk of cross contamination. The exhaust air to be recycled should be HEPA
filtered (high-efficiency particulate air-filtered) to remove airborne particles before it
is recycled; the extent and efficiency of filtration should be proportional to the
estimated risk.
Air that does not originate from animal use areas but has been used to ventilate
other spaces (e.g., some human-occupancy areas and food, bedding, and supply
storage areas) may be recycled for animal space ventilation and might require less-
intensive filtration or conditioning than air recycled from animal use space.
Toxic or odor-causing gases, such as ammonia, can be kept within acceptable limits
if they are removed by the ventilation system and replaced with air that contains
either a lower concentration or none of these gases. Treatment of recycled air for
these substances by chemical absorption or scrubbing might be effective; however,
the use of nonrecycled air is preferred for ventilation of animal use and holding
areas. The use of HEPA filtered recycled air without gaseous filtration (such as with
activated-charcoal filters) can be used but only that:
• Room air is mixed with at least 50% fresh air (that is, the supply air does not
exceed 50% recycled air).
• Recycled air is returned only to the room or area from which it was generated,
except if it comes from other than animal housing areas.
• Recycled air is appropriately conditioned and mixed with sufficient fresh air to
address the thermal and humidity requirements of animals in that space.
See applicable commentary on the previous
page.