542 



APPENDIX 



one satisfactory for mouse rooms. It is best to consult designers who have had experi- 

 ence in providing satisfactory animal room ventilation or who are competent enough 

 to provide a design to maintain conditions selected by the investigator or breeders. 

 Separate ventilation systems should be provided for each room to provide better 

 containment of health problems. All air introduced should be directly from outside, 

 although it is possible to recirculate up to 25-35 per cent of the air under certain con- 

 ditions (extremely cold outside temperatures) without encountering odor problems 

 from urine and fecal material. 



Fig. 86. Mouse rearing room at r. b. jackson memorial laboratory. 



To prevent introduction of dust particles carrying bacteria or viruses, the air 

 intake ducts should be provided with glass-wool filters capable of removing particles 

 as small as 0.2 microns in size or some similar system for accomplishing this. The 

 arrangements of relative air pressures in mouse rooms and accompanying corridors, 

 equipment-washing areas, or the like, will depend on the purpose of the unit. For 

 breeding mice or housing normal supplies, the plan should in general provide air flow 

 from the cleanest to the dirtiest area. This is accomplished by mounting equipment- 

 washing machines so that a solid wall separates the discharge end of the machines 

 (the cleanest area) from the feed-in area (the dirtiest area) . The air should then flow 

 from this clean area down corridors used solely for transportation of sanitized equipment 



