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Ventilation Design Handbook on Animal Research Facilities Using Static Microisolators 
Other countries’ standards are as follows: 
Australia: 5,000 ppm, STEL 30,000 ppm (1990); Federal Republic of Germany: 5,000 ppm, 
short-term level 10,000 ppm for 60 minutes, three times per shift (1989); Sweden: 5,000 ppm, 
15 -minute short-term level 10,000 ppm (1984); United Kingdom: 5,000 ppm, 10-minute STEL 
15,000 ppm (1987). 
1.4 Project Summary 
At project conception, NIH recognized that a comprehensive study of air movement, heat 
transfer, and contamination dispersal in the macro- and microenvironment in animal facilities 
could only be undertaken using Computational Fluid Dynamics (CFD). CFD is an advanced 
three-dimensional mathematical technique that can be used to compute the motion of air, water, 
or any other gas or liquid. If you were learning fluid dynamics as recently as, say 1960, you 
would be operating in the “two-approach world” of theory and experiment. However, the advent 
of the high-speed digital computer combined with the development of accurate numerical 
algorithms for solving physical problems on these computers has revolutionized the way we 
study and practice fluid dynamics today. The CFD approach provides a tool with which you can 
carry out numerical experiments and in this way undertake the comprehensive study envisaged. 
It was clear from the beginning that the disadvantage of this approach would be the vast amount 
of data generated for each and every simulation, compounded by undertaking many simulations. 
This project presents summaries of these data, in terms of mean cage values or mean values in 
the scientists’ breathing zpnes, to allow a designer or specifier to identify a satisfactory animal 
facility configuration. 
One of the major advantages of using CFD for such research is the confidence to simulate 
different configurations knowing that all conditions, except those being varied, remain constant. 
This makes comparison of CFD simulations much more reliable than comparison of 
experimental studies, where there is always uncertainty that all conditions are kept the same. 
However, it is important that all conditions are understood and correctly specified in the CFD 
simulation so the results it produces are as accurate as possible. In this study, inputs for the CFD, 
such as heat dissipation and surface temperature of the mice; in addition to moisture, CO 2 , and 
NH3 generation rates for mice; needed to be defined. Also the characteristics of the cages under 
study needed to be understood so an accurate mathematical model of a Microisolator cage could 
be built. As most of these data were not available from literature, an unprecedented set of 
experimental measurements was undertaken. 
Experimental work was undertaken with an instrumented shoebox cage and Microisolator placed 
in a wind tunnel. Using different approach velocities, the following were measured: 
