Deterioration of intra-cage ventilation and rising temperatures are common problems when filter caps are used to prevent cross-infection. Hypothesised that the use of a one-way air flow system (OWAS) to control air flow in the rack could also control increasing temperatures. Hence, experiments comparing the use of a one-way air flow system to that of a conventional ventilation system (CVS) were performed. For each system, the intra-cage temperatures - with and without the filter cap - for a varying number (zero, one, two, and three) of young adult rats were measured and found the greater temperature increases to be in the cage with the filter caps. Furthermore, temperature deviations were found to be related to the number of animals in a cage and the interface temperature gradient to be lessened when an OWAS for a filter-capped cage was used. This suggested improvement of the ventilation inside the cages.

KEYWORDS: calculating, microclimate, deteriorating, ventilation, temperature, filters, caps, air flow, experiment, comparing, measuring, temperature difference, laboratory animal housing, animal housing, once through air conditioning.