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Ventilation Design Handbook on Animal Research Facilities Using Static Microisolators 
to the cage will therefore have an impact on the ventilation within the cage; higher external flow 
velocities will result in better cage ventilation. The tabulated and the graphical representation of 
all the data is presented in appendix I: section 2.2, while the comparison between the CFD and 
experimental data, intended as a means of validating the CFD cage model, is given in section 
4.2. 1.2.2. 
The decay data is interesting in that it can be compared against previous work. In the case of a 
decaying concentration within a volume, the level of concentration remaining can be calculated 
from: 
C = Co e Al (4.4) 
Where: 
C - percent concentration, at time t 
Co - percent initial concentration, at t = 0 
X - Decay constant 
As the level of initial concentration varies from case to case, it is more convenient to normalize 
the decay such that the initial concentration is considered as 100 percent. The time taken to 
decay by a certain amount can then be tabulated. Table 4.1.02 below compares the time taken to 
decay the concentration by 90, 95 and 99 percent for the cage considered in Keller, White, 
Snyder and Lang (1989), and the parallel orientation cases considered in series set five. 
Table 4.1.02 Time taken to decay concentration by 90, 95 and 99 percent for Keller, White, 
Snyder and Lang (1989) cage, and series set five: parallel orientation results. 
Tunnel Velocity 
(fpm) 
Time to Decay (min) 
90 percent 
95 percent 
99 percent 
Keller, White, 
Snyder and Lang 
Paper @ 16 fpm 
(May 1989) 
18.27 
23.77 
36.54 
20 
16.69 
21.27 
33.37 
30 
12.38 
16.11 
24.76 
40 
11.29 
14.68 
22.57 
Further, figure 4.31 displays the comparison between the series set five: parallel orientation 
results and the results presented in Keller, White, Snyder and Lang (1989) with the concentration 
levels normalized such that the initial concentration is considered as 100 percent. 
