Ammonia and carbon dioxide concentrations in disposable and reusable ventilated mouse cages

This study compares resuable and disposable individually ventilated mouse cages in terms of the formation of intracage CO2 and NH3. Crl:CD-1(ICR) female mice were placed in either disposable or reusable ventilated cages in a positive pressure animal rack. Intracage CO2 and NH3 were measured once daily for 9 d; temperature and relative humidity were monitored for the first 7 d. Results indicated higher CO2 levels in the rear of the disposable cages and in the front of the reusable cages. This pattern corresponded to where the mice tended to congregate. However, CO2 concentrations did not differ significantly between the 2 cage types. Average CO2 levels in both cage types never exceeded approximately 3000 ppm. Intracage NH3 began to rise in the reusable cages on day 4, reached approximately 50 ppm by day 5 and by day 9 was greater than 150 ppm at the cages' rear sampling port while remaining at approximately 70 ppm at the front sampling port. Intracage NH3 levels in the disposable cages remained less than or equal to 3.2 ppm. Intracage temperature and relative humidity were approximately the same in both cage types. We concluded that the disposable ventilated cage performed satisfactorily under the conditions of the study.