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Ventilation Design Handbook on Animal Research Facilities Using Static Microisolators 
of bedding or frequency of cage changing; the room dimensions; or the efficiency of air 
distribution from the secondary to the primary enclosure. In some situations, the use of 
such a broad guideline might pose a problem. A secondary enclosure that contains few 
animals could be over-ventilated and would waste energy. Under-ventilating a secondary 
enclosure that contains many animals would allowing heat and odor accumulation. To 
determine more accurately the ventilation required, the minimal ventilation rate 
(commonly in cubic feet per minute) required to accommodate heat loads generated by 
animals can be calculated with the assistance of engineers. The heat generated by animals 
can be calculated with the average-total-heat-gain formula as published by the American 
Society of Heating, Refrigeration, and Air-Conditioning Engineers ASHRAE (1997). The 
formula is species-independent, so it is applicable to any heat-generating animal. Minimal 
required ventilation is determined by calculating the amount of cooling required (total 
cooling load) to control the heat load expected to be generated by the largest number of 
animals to be housed in the enclosure, any heat expected to be produced by non-animal 
sources, and heat transfer through room surfaces. The total-cooling-load calculation 
method can also be used for an animal space that has a fixed ventilation rate to determine 
the maximal number of animals, based on total animal mass, that can be housed in the 
space. Even though that calculation can be used to determine the minimal ventilation 
needed to prevent heat buildup, other factors, such as odor control, allergen control, 
particle generation, and control of metabolically generated gases, might necessitate 
ventilation beyond the calculated minimum. When the calculated minimal required 
ventilation is substantially less than 10 air changes per hour, lower ventilation rates might 
be appropriate in the secondary enclosure, provided that they do not result in harmful or 
unacceptable concentrations of toxic gases, odors, or particles in the primary enclosure. 
Similarly, when the calculated minimal required ventilation exceeds 15 air changes per 
hour, provisions should be made for additional ventilation to address the other factors. In 
some cases, fixed ventilation in the secondary enclosure might necessitate adjustment of 
sanitation schedules or a limit on animal mass to maintain appropriate environmental 
conditions. 
G.L. Riskowski, R.G. Maghirang, and W. Wang: Development Of Ventilation Rates And Design 
Information For Laboratory Animals Facilities, Part 2-Laboratory Tests, 1996, ASHRAE 
Transactions, V.102, Pt. 2, RP-730. 
Eight ventilation parameters for laboratory animal facilities were studied in a full-scale 
room ventilation simulator. They were room air exchange rate, diffuser neck diameter, 
diffuser type, number of returns, return location, cage type, room size and cage rack 
arrangement. Air exchange rates, velocities, and temperatures within the room and the 
cages were studied as well. Room airflow pattern and cage airflow patterns were 
determined using smoke tests. Cage conditions varied widely among cages within the 
same room. Cage type was the most important factor influencing cage conditions. Room 
air exchange rate, air velocity approaching the cage, number of returns, return location, 
and diffuser type did not significantly influence cage conditions in the ranges studied. 
