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On the subject of rodent isolator cage ventilation, the most widely used sources of performance criteria for research animal facility ventilation systems are the Guide for the Care and Use of Laboratory Animals, Institute of Laboratory Animal Resources (1996) and the American Society of Heating Refrigerating and Air Conditioning Engineers Applications and Fundamentals Handbooks. The Guide for the Care and Use of Laboratory Animals makes general recommendations for the ventilation of animal facilities, and it recognizes that the investigation of individual designs by techniques such as CFD may be necessary to ensure optimum performance.

The ventilation recommendations are often based on room air exchange. However, the cage ventilation rates may be inadequate in some cases and excessive in others depending on cage and facility design. Several studies have shown that covering cages with filter tops provide a protective barrier for rodents, and it reduces airborne infections and diseases, especially neonatal diarrhea. However it could also result in significant differences in micro environmental conditions like carbon dioxide, ammonia, temperature and humidity levels, due to changes in the air exchange with the room(room-cage coupling) caused by the cage cover. Another important factor in maintaining the cage environment is the type of bedding used and the frequency of change established for this bedding. Therefore, a comprehensive study of air movement, heat transfer, and contamination dispersal in the cage microenvironment would provide valuable information for the design of rodent cage ventilation systems. This study can be facilitated by using computational fluid dynamics (CFD). CFD is an advanced, three dimensional mathematical technique widely used to model the air motion, water transport, or the transport of any fluid. Several software codes are available for CFD modeling. This paper presents a CFD model for a conventional rodent isolator cage.

Using the CFD modeling, profiles of velocity, temperature, humidity and ammonia in the cage environment have been developed. A model has been developed to evaluate the effect of using corncob bedding on the moisture levels in the cage.