Abstract: Objective To dynamically assess the micro-environmental changes of the new type exhaust ventilated closed-system cage (EVC)for mice. Methods Based on the measurement of ventilation velocity and volume in EVC cages with mice, the air exchange rate were calculated. The parameters of noise, temperature, differential air pressure, relative humidity, micro-environmental ammonia concentration and macro-environmental ammonia concentration were detected continuously for a 7-day-cycle with wooden shaving bedding and for a 14-day-cycle with corncob bedding. Results The noise in two type EVC were 54.2±3.4 db and 55.6±4.1 db. The differential pressure between EVC and room were -23.1±9.2 Pa and -27.5±11.6 Pa respectively. Since the first day of caging change-cycle, the micro-environmental temperature, humidity and ammonia concentrations has raised gradually in cages. On the sixth day, ammonia concentration in two type of cages reached 1.28±0.08 mg/m³ and 1.33±0.15 mg/m³ respectively with wood shaving beddings, the temperature were 23.5±0.27 ℃ and 22.8±0.15 ℃ respectively, the humidity were 67.8%±2.2% and 70.2%±1.1% respectively. On the twelfth day, ammonia concentration in cages reached 1.95±0.46 mg/m³ and 2.17±0.33 mg/m3 with corncob beddings, the temperature were 23.8±0.4 ℃ and 24.1±0.2 ℃, and the humidity were 70.3%±1.8% and 69.6%±1.8% respectively. Conclusions Based on the conditions of current experiment, during 6-day and 12-day caging change-cycle respectively, the micro-environmental parameters, such as: noise, differential air pressure, temperature, humidity and ammonia concentrations met the GB14925-2010 requirements. EVC system with corncob bedding are highly recommended to maintain a stable micro-environment, that could be used in animal research and animal production.

Key words: Temperature, Relative humidity, Ammonia concentration, Microenvironment