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Ventilatiom Design Handbook on Animal Research Facilities Using Static Microisolators 
Table 2.16 Basecase (Case 01): NH3 Concentrations (ppm) over a 10-Day Cycle in the Cages 
The average NH 3 concentration in the cages rises from around 1 ppm to over 38 ppm by day 10. 
By day 5 the average cage NH 3 concentration is over 10 ppm. The NH 3 concentration in the 
worst single cage in the room (shown in the Max line in table 2.16) is approximately 50 percent 
higher than the average. Clearly in the latter part of the cycle the cages on average exceed the 25 
ppm critical level for NH 3 by day 8 and the worst cage exceeds this value by almost 2 days 
earlier. That these values are not even higher is due to the good ventilation performance of the 
basecase room and the relatively low relative humidity values. 
In a practical scenario where the bedding is changed after four days the room would not be 
considered smelly, although the individual cages would be. 
The summary sheets for each run also contain three histograms that show the variation of RH 
concentration and temperature in the cages. The histograms show the number of cages 
(frequency) that have values which fall in the range between two values marked on the horizontal 
axis, with only the upper value indicated. For example, in figure 2.34 the column labeled 67 
indicates that 35 cages have an RH between 66 percent and 67 percent. The concentration 
histogram can be converted to CO2 and NH 3 concentrations by multiplying the kg/kg values 
given in the chart by a conversion factor. The conversion factors are given for the basecase in 
table 2.17 below: 
Table 2.17 Conversion 
Day 
CO2 
nh 3 
1 
785000 
418 
2 
785000 
795 
3 
785000 
1225 
4 
785000 
1922 
5 
785000 
2848 
6 
785000 
3443 
7 
785000 
8409 
8 
785000 
8483 
9 
785000 
8442 
10 
785000 
11384 
■actor between kg/kg and ppm for CO2 and NH 3 Concentrations 
The plots for the basecase are shown below. These show virtually a standard Gaussian bell- 
shaped distribution around the mean values. Comparison of these histograms for the different 
