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Ventilation Design Handbook on Animal Research Facilities Using Static Microisolators 
either a Reemay filter insert or when the two different frames were compared for 
temperature, CO2, relative humidity, or NH3. Daily NH3 levels detected in study V 
were as high as 450 ppm with humidities over 90 percent RH in individual cages 
from the Microisolator and Micro-Barrier systems. Detector tubes with the 
broader range of 50 to 900 ppm of NH3 were used for this study. 
Lynn S.F. Keller, William J. White, Michael T. Snider and C. Max Lang: An Evaluation of Intra- 
Cage Ventilation in Three Animal Caging System, 1989, Lab. Anim. Sci., 39:237-242. 
Although temperature and relative humidity have been quantified and their effects on 
research data studied, few studies have measured the air turnover rates at cage level. We 
evaluated the air distribution and air turnover rates in unoccupied shoebox mouse cages, 
filter-top covered cages, and shoebox mouse cages housed in a flexible film isolator by 
using discontinuous gas chromatography/mass spectrometry apd smoke. Results showed 
that air turnover was most rapid in the unoccupied shoebox mouse cage and slowest in 
the filter-top covered cage. Placing mice in the filter-top covered cage did not 
significantly improve the air turnover rate. Although filter-top covered cages reduce cage- 
to-cage transmission of disease, the poor airflow observed within these cages could lead 
to a buildup of gaseous pollutants that may adversely affect the animal's health. 
T.J. Van Wrinkle, M.W. Balk: Spontaneous Corneal Opacities in Laboratory, 1986, Lab. Anim. 
Sci., 36:248-255; G.L Keller, S.F. Mattingly, F.B. Fnapke, Jr.: A Forced Air Individually 
Ventilated Caging System for Rodents, 1983, Lab. Anim. Sci., 33:580-581; G.R. Gale, A.B. 
Smith: Ureolytic and Urease- Activating Properties of Commercial Laboratory Animal Bedding, 
1981, Lab. Anim. Sci., 31:56-59; J.R. Lindsey, M.W. Connor, H.J. Baker: Physical, and 
Microbial Factors Affecting Biological Response in Animal Housing, 1978, National Academy 
of Sciences, 31-43; M.R. Gamble, G. Clough Ammonia Build-Up in Animal Boxes and its Effect 
on Rat Tracheal, Lab. Anim. (London), 10:93-104,1976. 
Carbon dioxide and ammonia are the major gaseous pollutants generated by animals and 
animal waste within the cage. Ammonia levels in an animal's environment are dependent 
on fecal bacteria flora, population density, frequency of bedding changes, type of bedding 
material, cage design, temperature, humidity, cage sanitation, ventilation, and the animal's 
level of activity. 
