A positive, individually ventilated caging system: a local barrier system to protect both animals and personnel

Abstract

Most local barrier systems are designed primarily either to protect animals from airborne contamination (exclusion) or to ensure the safety of personnel (hazard containment). Few, other than isolators, are able to cope with the often conflicting demands to do both. The Positive Individually Ventilated system (PIV), which provides pressure adjustable, individual supply and exhaust ventilation to each cage has been tested with this in mind as well as the need to ensure that environmental conditions comply with the requirements of the Home Office Code of Practice (CoP). The results indicate that when compared with traditional open racking the system can reduce both the risk of animals becoming contaminated by airborne infection from the room and the risk of aeroallergens escaping from the cages into the room air. At the same time, environmental conditions within the cages are both less variable and less stressful to the occupants. Conditions of air temperature, relative humidity, ventilation rates, light intensity and (with appropriate air handling) sound levels, all comply with or are better than those required by the CoP. Even with the room air change rate set at only 8/h (8 ac/h) the air distribution system results in draught-free cage ventilation rates of around 50-120 ac/h. This means that with at least the PIV exhaust(s) linked directly into the air conditioning system of the building, the size of the latter and its associated running costs can be reduced by around 50%; this energy saving concept has been approved in principle by the Home Office. Additional benefits include the fact that bedding is kept much drier allowing further cost savings in bedding and associated labour costs. The system is thus beneficial to the animals in protecting them from airborne infection and other stresses. By providing a less variable environment it also helps to minimise the sort of interference with experiments which can arise from that source. Similarly, in accordance with the aims of 'The Control of Substances Hazardous to Health Regulations' (COSHH 1988) and the Health & Safety Executive (HSE 1990), by reducing dust levels in the room air, including allergens, it is also beneficial to the personnel working in the animal rooms.

Microbiological monitoring of laboratory mice and biocontainment in individually ventilated cages: a field study

“…Over recent years, the use of individually ventilated cage (IVC) rack systems in laboratory rodent facilities has increased. In a typical IVC rack, each cage receives high efficiency particle absorbance (HEPA)-filtered air which, when supplied under positive pressure, protects the animals in the cages from airborne infectious or other noxious particulate agents present in the environment (Cunliffe-Beamer & Les 1983, Lipman et al 1993, Clough et al 1995, Lipman 1999. Similarly, the exhaust air from the cages is normally also HEPAfiltered before it is returned into the room environment.…”

Decontamination of a barrier facility using microisolator cages and provisional partitioning

“…The infection risk was further enhanced by the fact that it was not possible to completely separate the HVAC systems of the two newly established units or to establish adequate two-way personnel locks. Suboptimal personnel and HVAC barrier conditions have previously been shown to play a critical role in protection against pathogens 13,14 . However, our results show that it is possible to compensate for these suboptimal conditions and achieve success by using filter-top cages and servicing cages in cage-changing stations.…”

Rodent and Germplasm Trafficking: Risks of Microbial Contamination in a High-Tech Biomedical World

“…In a typical IVC rack, each cage receives high-efficiency particulate air (HEPA)-filtered air. Mice are kept under positive pressure to protect them from airborne infectious or other noxious particulate agents in the environment (Clough et al 1995;Cunliffe-Beamer and Les 1983;Lipman et al 1993;Lipman 1999). Similarly, the exhaust air from the cages is HEPA-filtered before being returned to the room environment or to the heating, ventilation, and air conditioning (HVAC) system.…”