Use of portable filter units to control the animal house environment

The application of portable recirculating filter units to the control of laboratory animal house environments was investigated. Under practical conditions such a unit effected reductions in the ammonia level and bacterial content of the atmo-sphere of a room housing rats. The provision of a controlled atmospheric environ-ment appropriate to the requirements of individual species is well recognized as of prime importance in the successful management oflaboratory animals (Clough, 1976; Lane-Petter, 1976). Since the provision of such an environment usually depends upon frequent changes of heated and filtered outside air, with or without humidity control, it is a major cost item in the construction and running of most animal houses. Temperature requirements for commonly used laboratory animals range between 16°C and 25°C and recom-mendations for ventilation rates may be as high as 18 air changes per hour (Alschuler, 1963) depending on the stocking density. The use of efficient recirculating air purifiers, perhaps com-bined with heating and cooling elements, would greatly reduce the cost of environmental control in animal houses. When the ventilation of an animal room is inadequate the temperature and humidity rise and the levels of ammonia and animal odour in the atmosphere increase, as do the dust and micro-biological content. These factors predispose to the spread of airborne infections in the animals and also produce hazardous and unpleasant working conditions for personnel. A portable chemosorbent filter.unit has been successfully used to reduce odours in hospital wards (Lawrence, Lilly & Wilkins, 1981) and a recirculating particulate filter was shown to reduce aerial bacterial counts and clinical respiratory disease in calf houses (Pritchard et al., 1981). The application of portable recirculating filters to laboratory animal units appears not to have been described. In this paper the effects of such a filter unit on the atmosphere of a poorly ventilated room containing rats are recorded