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Ventilation Design Handbook on Animal Research Facilities Using Static Microisolators 
Figure 3.41 Comparison of Mean Breathing Zone NHj Concentrations (ppm) 
The radial and low induction diffusers show a reduction in cage CO2 and NH3 concentrations in 
the cages with clearly better ventilation through the racks (and cages) in this perpendicular 
orientation. The in-room breathing zone values show similar or slightly increased CO2 and NH3 
concentrations. 
Cases 48 to 52 were run with different positions for the change station (swapped with particular 
racks) and cases 90 to 92 were run with all five racks positioned on one wall rather than split two 
on one wall and three on the other. Again, variations in CO 2 and NH3 concentrations for both the 
cages and the room are small. 
In conclusion, apart from the improvement in cage ventilation for the radial and low induction 
diffusers when the racks are perpendicular to the walls, no particular advantage or disadvantage 
in any orientation or rack layout can be seen. 
3.1.6 Density of Cages 
Cases 31 to 36 were run with double the number of cages on each rack. This meant a total of 420 
cages were present in the room. To provide easy access to all the cages it was necessary to use 
only rack orientations that were perpendicular to the side wall (i.e., into the room not parallel to 
the side walls). 
Figures 3.42 to 3.45 show comparisons of CO 2 and NH3 concentrations for the three supply 
diffuser types with ceiling and low level exhausts. 
