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Ventilation Design Handbook on Animal Research Facilities Using Static Microisolators 
• Study I: 
The temperature range for all caging systems was 75.5 °F ± 0.5 °F. 
Carbon dioxide: The Microisolator and Micro-Barrier systems averaged greater than 
2,200 ppm more CO 2 than those in the molded polyester system which was 2,900 
ppm greater than the control. The control cage CO 2 levels of 316 ppm approximated 
the 279 ppm in the macro environment. 
Relative humidity: Microenvironmental humidity levels in the Microisolator and 
Micro-Barrier systems averaged greater than 20 percent RH higher than in the control 
cages. RH in one cage reached over 85 percent. 
Ammonia: Weekly NH3 levels in the control cages were 1.6 ppm and the molded 
polyester systems were 0.9 ppm. Weekly levels for the Microisolator and Micro- 
Barrier systems were 139.1 ppm and 162.8 ppm of NH3 respectively. By day 4, one of 
the Micro-Barrier cages was already at 260 ppm NH 3 , the maximum level attainable 
for the sampling tube. By day 6, seven of eight cages from the Microisolator and 
Micro-Barrier systems contained greater than 200 ppm of NH 3 . 
• Study II: 
There were no significant temperature variations among caging systems at 20 percent 
macro environmental humidity. 
Carbon dioxide: Similar trends, as in study I, were observed for CO 2 levels among 
caging systems at the lower room humidity. No significant differences were observed 
when compared to study I. 
Relative humidity: There was a proportional 15 to 30 percent RH decrease in 
microenvironmental RH levels in all caging systems when macroenvironmental 
humidity was lowered to 20 percent RH. Similar trends were observed among caging 
systems when compared with humidity levels in study I. 
Ammonia: Weekly intracage NH, levels, which averaged 139.1 and 162.8 ppm for the 
Microisolator and Micro-Barrier caging systems respectively, when macro 
environmental humidity was 50 percent RH, were reduced to four and 17 ppm of NH3 
for these systems when room humidity was reduced to 20 percent. Ammonia 
detection at the lower humidity was not evident until day 7. There were no detectable 
NH3 levels in any of the molded polyester or control cages at 20 percent 
macroenvironmental humidity. 
