§ 627.56 - Ventilated cage enclosures.

There are a number of cage-ventilated enclosures in which infected animals may be housed at levels corresponding to the various classes of biological safety cabinets. A brief description of four different types of animal ventilated cages is given below. This is not a complete description of all the different animal ventilated cages available. The proper functioning of these will be tested initially, upon each connection to exhaust sources, and at least annually. The inward flow rates on the partial containment systems and pressure checks on the total containment cages will be performed. Prior to selecting such equipment, an evaluation of the function and the equipment should be made, and the methods for testing and decontamination should be analyzed and documented.

(a) Filter-top cages. Small laboratory animal polystyrene or polycarbonate cage bottoms are fitted with a dome shaped glass fiber or polyester filter cage cover. The dome shaped filters help reduce the dissemination of aerosols, and the spread of infectious agents. Adequate ventilation around cages fitted with a dome shaped filter is essential since they may contain elevated ammonia and carbon dioxide levels, and high temperature and humidity. Ventilation recommendations in the NIH publication 86-23, 1985 “Guide for the Care and Use of Laboratory Animals” will be followed.

(b) Forced ventilation cages. This is a small HEPA-filtered cage connected to a centralized exhaust system. A minimum airflow of 0.03 m3 /min per cage is required. Ventilation rates may vary with the size of the cage, and the number and type of animals being housed.

(c) Cubicle-type isolation cage. This is a partial containment unit which holds several animal cages. This unit is a negative pressure HEPA-filtered stainless steel cage. A minimum airflow of 0.3 m3 /min per cage is required for a 0.24 m3 unit. Ventilation rates may vary with the size of the cage and the number and type of animals being housed.

(d) Total containment cage. This unit is a negative pressure or positive pressure HEPA-filtered stainless steel cage which has the filters incorporated into the design. It is halogen gas-leak tight and can be considered a Class III biological safety cabinet. A minimum airflow of 0.3 m3 /min per cage is required for a 0.24 m3 unit. Ventilation rates may vary with the size of the cage, and the number and type of animals being housed.