A novel vented microisolation container for caging animals: Microenvironmental comfort in a closed-system filter cage

We designed a closed-system cage with vent ports that would allow continuou s airflow in the occupied cage to ensure adequate ventilation and gas excha nge, In this system, the metabolic heat loads of mice generate upward therm al air currents, Heat exits via the exhaust port, and room air enters via t he intake port, providing adequate ventilation. Simulations based on comput ational fluid dynamics (CFD) helped us to optimize the cage's design, CFD s imulations and smoke visualizations with a feeder-trough assembly illustrat ed the one-pass air circulation pattern and the lack of air recirculation, turbulence, and dead air space in our system, We used hot-film anemometry a nd smoke-test methodologies to show that adequate ventilation was provided; In a room with still air (0 air changes per hour [ACH]), a cage fitted wit h double wire-cloth filters (40 mesh size) and occupied by five mice has at least 12 ACH, whereas the same cage occupied by one mouse has 6 ACH. After five mice had occupied the cage for a week, its average temperature was 0. 5 degrees C, relative humidity was 34%, and ammonia concentration was 3 ppm higher than that of the room. Our novel vented microisolation cage provide s adequate intracage ACH, isolates mice from environmental contaminants, an d contains allergenic particles within the cage in an environment appropria te for the species.