Share thisVentilated caging systems have been a primary contributor to the rapid advances of biomedical research in recent decades. Their increased usage has also been an indirect contributor to energy savings for many institutions for a variety of factors.
The following paragraphs will briefly review a few of the factors that have led to the increased usage of ventilated caging systems as they relate to energy efficiency.
The original Horsfall-Bauer isolation units were developed in the 1940s. Those units were basically a box that enclosed a primary animal cage. The boxes were supplied with filter material on the supply and exhaust vents. Air flow was obtained by a fan on the exhaust port that drew air through the exhaust filter, therefore creating a negative air-flow environment.
The first rodent racks with positive supplied, HEPA-filtered air was introduced in 1978. This system supplied a positive air flow to each cage but also included exhaust fans with HEPA filters on both the supply and the exhaust. The air flow on this system could be adjusted to create either a positive or negative environment depending upon the research requirements. Since these concepts were introduced to the biomedical community, a variety of air flow configurations have been used and new systems are still being introduced into the market which utilize building supply and/or exhaust. Many of these systems are also equipped with HEPA filtration on the supply and/or the exhaust.
The concept of treating the micro-environment of the animal cage, as opposed to the macro-environment of the room, vastly changed laboratory animal care. Every aspect of husbandry, from facility design to scientific design, was impacted by the introduction of these systems. Research programs have gone from supplying 15 air changes per hour (ACH) in the macro-environment (animal room), to 50–60 ACH in the micro-environment (the primary cage). Providing 50–60 ACH of HEPA-filtered air directly into the cage not only provides a healthier environment, but relieves the building HVAC of a major air supply and exhaust burden. The requirements for cubic feet of air supply are reduced from the large cubic feet needs of the room to the relatively small requirement of individual cages. The minimum room recommendation of 15 ACH can be supplied from the building system while the increased performance of 50–60 ACH can be obtained from other sources and supplied directly to the cage without burdening the building system. As the population density of animal rooms increases, the supply of clean air and removal of odors and danders increases tremendously. Thus, the use of ventilated cages systems becomes more logical and efficient in that the use of floor space is maximized while the air supply is directed to the small environment of the animal enclosure.
As an example of efficiency, assume that we have a theoretical room that is 10’x 10’x 10’ or 1000 cubic feet. If we wish to supply 60 ACH, we would multiply the 1000 cubic feet by the 60 ACH and arrive at a total of 60,000 cubic feet of air needed to be supplied by the central HVAC system.