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Ventilation Design Handbook on Animal Research Facilities Using Static Microisolators 
The slot diffuser also shows little variation, with a small increase in cage concentrations and 
slightly larger increases in room concentrations, going from negative to positive pressurization. 
The low induction diffuser shows increases in room concentration but decreases in cage 
concentrations. 
Again it is difficult to make a general recommendation. The effects seem small and dependant on 
the actual details of the configuration under study. 
3.1.5 Orientation of Cage Racks in Room and Rack Grouping 
Cases 19 to 24 were run with the five racks positioned perpendicular to the side walls rather than 
parallel to them. They should be compared with cases 1, 3, 4, 6, 7, and 9. This orientation 
removes the central open area in the room for the scientists as the racks overlap. However, data 
for the scientist’s breathing zone are still reported although this is somewhat smaller. The 
analysis excluded a 0.15m (6”) space around each cage. 
Figures 3.38 to 3.41 show comparisons for the three diffuser types with ceiling level exhausts for 
single density racks parallel and perpendicular to the walls. 
Figure 3.38 Comparison of Mean Cage CO 2 Concentrations (ppm) 
