Determination of Air Distribution, Exchange, Velocity, and Leakage in Three Individually Ventilated Rodent Caging Systems.

Methods for characterizing the design and operation of ventilated caging systems were investigated to define and quantify differences in air distribution, exchange, velocity, and leakage in 3 commercially available systems-units 1, 2, and 3. Intracage air distribution patterns were determined by visually observing smoke dispersion patterns after release at 3 intracage locations from a TiCl4, smoke stick in 3 cages/system. Smoke distribution was rapid and complete in unit 1; visible leakage of smoke from the cage was observed. Smoke distribution in unit 2 was the slowest of all systems tested, and mixing was not complete; no visible leakage was observed. The smoke distribution in unit 3 was rapid and complete, but not as fast as in unit 1; no smoke leakage was observed. Intracage air exchange rates per h (ACH) were calculated by determining sulfur hexafluoride (SF6) decay curves at 8 predetermined detection points after introduction of SF6 into the supply air stream of 1 cage/system. Mean SEM ventilation rate were 65 19,42 32, and 79 21 ACH for units 1,2, and 3, respectively. Intracage airvelocitywas measured at predetermined points within the cage, using a thermoanenometer. Mean SD air velocity was 36 18 and 37 12 linear feet/min for units 1 and 3. Air velocity was below the detection limit (< 10 linear feet/min) of the thermoanenometer for unit 2. Air leakage was determined qualitatively by measuring the concentration of SF6 escaping from select cages for each system. Leakage of SF6 was detectable from units 1 and 3, but not detectable from unit 2. Standardized testing methods were used in this study so that other users can adequately compare systems and understand more fully the advantages and limitations of particular systems.