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Ventilation Design Handbook on Animal Research Facilities Using Static Microisolators 
more comfortable environment for the mice (Gordon, Becker, and Ali, 1997) the high room 
temperature may be uncomfortable for the scientists and animal caregivers working in the 
room. 
• Ceiling or high-level exhausts tend to produce lower room temperatures when compared to 
low-level exhausts. All CFD models were designed to have 22 °C (72 °F) for a given supply 
air temperature at the room exhausts. There were also a small number of tests run with high 
supply temperatures. These studies indicate that low-level exhausts are less efficient at 
cooling the room and will be more expensive to operate. 
• Low-level exhausts appear to ventilate the cages slightly better than ceiling or high-level 
exhausts when the cages are placed parallel to the walls. Improvement was up to 27 percent 
for the radial diffuser, 4 percent for the slot diffuser, and 25 percent for the low induction 
diffuser. See figure 0.4. The ammonia concentration in the cages (see figure 0.5) appears to 
be even further reduced although this is due to the higher temperatures in the low-level 
exhaust cases when compared to the ceiling and high-level exhausts which act to reduce the 
relative humidity and the ammonia generation rate. 
Figure 0.4 Mean CO 2 concentration (ppm) in cages for Radial, Slot and Low Induction 
supply diffusers with Ceiling, High-Level and Low-Level Exhausts 
