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Ventilation Design Handbook on Animal Research Facilities Using Static Microisolators 
2.32 Quantitative Analysis 
Although visual inspection of the CFD results can give much insight into the conditions within a 
room, it does not allow an efficient comparison of one room simulation to another. In order to 
allow us to compare the various room models it was necessary to define some quantitative 
measures for the cages and the room as a whole. The following parameters were considered 
important in this study: 
Cages: 
• Mean temperature in each cage 
• Mean relative humidity in each cage 
• Mean CO 2 and NH 3 concentrations in each cage 
The mean value for each cage was also further averaged to provide a single value representing 
the “average cage” in the room. These values were calculated for the “occupied zone” of each 
cage, i.e., the region below the wire mesh grille, which represents the environment the mice 
would normally experience. 
Room: 
• Mean breathing zone temperature 
• Mean breathing zone relative humidity 
• Mean breathing zone CO 2 and NH 3 concentrations 
The breathing zone is defined as a region in the center of the room between the racks of cages 
and between the door and change station, at a height from 1.50m to 1.80m (4’ 11” to 5’ 1 1”). 
These parameters were derived from the many millions of numbers produced by the CFD 
simulations as follows: 
Temperature: 
The mean temperature was derived from the actual temperature in each grid cell of the 
CFD simulation by multiplying the temperature by the volume of the grid cell and 
dividing by the total volume of the space (the cage volume or the “breathing zone” 
volume in the room). 
Relative Humidity: 
The relative humidity was calculated by first determining the moisture content in each 
cage by taking the mass fraction values calculated in the CFD and multiplying by the ratio 
of the experimentally determined moisture generation rate (0.83 g/hr) to the nominal 
