Volume I - Section I - Introduction 
Pa 2 e 1-15 
Academic Press, Inc., 713-718. 
Ammonia is produced by enteric bacteria through two possible mechanisms of enzymatic 
activity. Bacterial ureases can catalyze the hydrolysis of urea to ammonia and carbamate. 
A second series of enzymes, D-and L-amino acid oxidases can deaminate amino acids to 
their corresponding keto acid and ammonia. 
Y. Zhang, L.L. Christianson, G.L. Riskowski, B. Zhang, G. Taylor, H.W. Gonyou, and P.C. 
Harrison: A Survey of Laboratory Rat Environments, 1992, ASHRAE Transactions: Symposia, 
98(2)247-253. 
A survey of laboratory animal environmental conditions in seven laboratory rat rooms 
was conducted. These rooms were designed and operated according to the ELAR (1985) 
guidelines, which recommended at least 10 ACH. Room air changes varied from 1 1 to 24 
ACH, room air ammonia levels were under 0.5 ppm, and macroenvironmental conditions 
were considered satisfactory. However, cage air quality conditions and ventilation rates in 
typical rat cages may be “inadequate, which” or “inadequate and could” compromise the 
rat's respiratory systems. For those same rooms, ammonia levels ranged from negligible 
to 60 ppm in the cages. The authors noted that designs based only on room air changes 
may not be adequate to achieve desired conditions in the animal cages. 
Brian F. Coming and Neil S. Lipman: A Comparison of Rodent Caging Systems Based on 
Microenvironmental Parameters, 1991, Lab. Anim. Sci., 40:498-508. 
Four different mouse caging systems were evaluated for micro environmental 
temperature, carbon dioxide, relative humidity (RH) and ammonia levels during a 7-day 
testing period. All caging systems evaluated had polycarbonate bases and consisted of 
either a molded polyester (MP) filter lid, one of two different polycarbonate filter lids, or 
no filter lid which served as a control. At 50 percent macro environmental RH (study I), 
all systems maintained an intracage temperature of 75.5 °F ± 0.5 °F. Both polycarbonate 
systems averaged > 2,200 ppm of carbon dioxide, more than the MP system and the 
controls. When compared with RH in the control cages, RH levels averaged over 20 
percent and five to eight percent RH greater in the polycarbonate filter lid systems and the 
MP system, respectively. There were no appreciable ammonia levels in either the MP or 
control systems. In the polycarbonate filter lid systems, ammonia levels were detectable 
on day 4 and were > 200 ppm by day 6. At 20 percent macro environmental RH (Study 
IT), there was a proportional 15 to 30 percent RH decrease from study I levels. Ammonia 
levels were undetectable in any system until day 7 and averaged only 17 ppm in one of 
the polycarbonate systems. Minimal differences were observed in studies m, IV and V 
when pine shavings were used instead of hardwood chips, a CD-I stock instead of a 
DBA/2J strain, and different grades of filter inserts in the polycarbonate systems, 
respectively. 
