Volume I - Section II - Animal Room Variations 
Page II - 33 
source rate (0.76g/hr). This additional water content was then added to the moisture in the 
supply air (8.40e-3 kg water per kg air, 50 percent RH at 22.2 °C (72.0 °F) for all cases 
except those at very low (5 ACH) air supply rates where 5.40e-3 kg/kg was used. The RH 
can be determined from a Psychrometric chart from the total moisture content of the air 
and the temperature of the cage 
C0 2 (ppm): 
The ppm concentrations for C0 2 in air were calculated directly from the simulated mass 
fraction information in the CFD results by multiplying the mass fraction value by the ratio 
of the actual generation rate to the nominal generation rate (0.9 / 0.76) and the ratio of 
molecular weights (29/44). 
NH 3 (ppm): 
The concentration of NH3 was also derived from the mass fraction values calculated in 
the CFD simulations, but the process was more complicated. First, the relative humidity 
in every cage is calculated as described above. The average RH for all the cages was then 
used to calculate the generation rate of NH3 for each day in the 10-day cycle using the 
experimental data shown in section 4. 1.2. 8 . 2. RH values below the minimum range (61 
percent) for the experimental data used the generation rate of the minimum value. RH 
values above the maximum range (8 1 percent) used the generation rate of the maximum 
value as it was deemed unsafe to extrapolate outside the ranges. Once the generation rate 
to be used was determined, the ppm concentration of NH 3 was calculated in the same 
manner as the C0 2 concentrations. 
As each day had a different NH3 generation rate, the NH3 concentrations are different on 
each day. However as the underlying mass fraction information and RH information does 
not change on a daily basis in the simulations, room performance can be compared by 
using the results for any of the 10 days. For ease of comparison, results are presented for 
day 4, which corresponds to the day most widely used to change the bedding in the mice 
cages. 
In addition to the mean values it is also possible to get minimum and maximum values. In most 
cases the minimum value is not interesting but the maximum value may provide information. In 
particular, the maximum NH3 concentration can be important, as it is not always necessary for 
the room average value to be so high that the scientists can detect it by smell. A high value in a 
single location could be enough. 
The results for each room are summarized in Volume n. 
