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Ventilation Design Handbook on Animal Research Facilities Using Static Microisolators 
housed mice prefer a temperature of approximately 29 to 30 °C (84 to 86 °F), which is 
warmer than the standard housing temperature of 22 to 24 °C (72 to 76 °F). This suggests 
that groups of mice may experience cold stress under standard housing conditions. 
A comprehensive study of air movement, heat transfer, and contamination dispersal in the 
macro- and microenvironment in animal facilities could only be undertaken using computational 
fluid dynamics (CFD). CFD is an advanced three-dimensional mathematical technique used to 
compute the motion of air, water, or any other gas or liquid. All conditions must be correctly 
specified in the CFD simulation in order to obtain accurate results. 
All the inputs for the CFD had to be defined for this study, including heat dissipation and surface 
temperature of the mice; and moisture, CO 2 , and NH3 generation rates for mice. Defining this 
data required an extensive series of experimental measurements using sets of outbred female 
mice (HSD-ICR) with an initial age of four weeks. The mice were placed in microisolator cages 
with hardwood (beta chip) shaving bedding for a 13-day period. In addition to providing specific 
data and recommendations this document details experimental and numerical procedures that can 
be used for other species. 
Cage characteristics needed to be fully understood so an accurate mathematical model of a 
microisolator cage could be built. As most of these data were not available from literature, an 
unprecedented set of experimental measurements was undertaken. Without this foundation of 
accurate experimental data the CFD analysis of the rooms would have had limited value. 
On the subject of ventilation the most commonly accepted source of performance criteria for 
research animal facility ventilation systems is the Guide for the Care and Use of Laboratory 
Animals, Institute of Laboratory Animal Resources (1996) and the American Society of Heating 
Refrigerating and Air Conditioning Engineers Applications and Fundamentals Handbooks. The 
Guide makes general recommendations for ventilation of animal facilities and recognizes that 
investigation of individual designs by techniques such as CFD may be necessary to ensure 
optimum performance, e.g. “The guideline of 10-15 fresh-air changes per hour has been used for 
secondary enclosures for many years and is considered an acceptable general standard. Although 
it is effective in many settings, the guideline does not take into account the range of possible heat 
loads; the species, size, and number of animals involved; the type 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 by overventilating a secondary enclosure that contains few animals and thereby wasting 
energy or by underventilating a secondary enclosure that contains many animals and thereby 
allowing heat and odour accumulation.” 
Ventilation recommendations are often based on room air exchanges. However, cage ventilation 
rates may be inadequate in some cages and excessive in others depending on cage and facility 
design. Recommendations for room ventilation rates of 10 to 15 air changes per hour (ACH) are 
an attempt to provide adequate ventilation for the room and the cages. This recommendation is 
based on the assumption that adequate ventilation in the macroenvironment provides sufficient 
