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Ventilation Design Handbook on Animal Research Facilities Using Static Microisolators 
The results do indicate that the cages are not significantly better ventilated at higher flow rates. 
The rooms are better ventilated up to 20 ACH as would be expected because there is more fresh 
air available to dilute the gases produced by the mice. 
The animal loading in the room is clearly significant. The 5 ACH supply rate in the room with 
single density cage racks (case 29) produces less than 50 percent of the room CO 2 concentration 
compared with the 5 ACH with the double density racks (cases 62 and 66). Since 10 ACH seems 
acceptable for day 4 NH3 concentration in the cages of the double density rooms, and 5 ACH is 
acceptable for NH3 concentrations in the cages of single density rooms, the airflow required in 
the room is best at 0.85 cfm (4.01e-4 m 3 /s) per cage of five mice or lOOg body weight of mice 
(see also section 3.2 below). 
3.1.3 Change Station Design and Status 
Cases 10 to 15 were run with the change station switched off and no heat generation or 
recirculated air. These should be compared with cases 1, 3, 4, 6, 7, and 9. Figures 3.29 to 3.32 
show comparisons of CO2 and NH3 concentrations for the three supply diffusers with ceiling 
level exhausts and the Thoren change station in operation (on) and also with it present but not 
operating (off). 
Figure 3.29 Comparison of Mean Cage CO 2 Concentrations (ppm) 
