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Ventilation Design Handbook on Animal Research Facilities Using Static Microisolators 
4.1.2 CO 2, NH 3 , H2O and Heat Generation Measurements at Low and High 
Humidities 
4. 1.2.1 Introduction 
This study was conducted at the Bioenvironmental Engineering Research Laboratory (BERL) 
and was intended to determine typical mass generation rates of CO2, H2O, and NH3, and 
consumption of O2 of mice in shoebox cages with bedding at two environmental relative 
humidities (35 percent and 75 percent). To determine the gas generation rates, animals and their 
cage habitat were placed within enclosed chambers (open-system calorimeters) with precisely 
controlled fresh air exchange rates. Cage bedding was not changed for longer than normal 
periods (10 days) to allow ammonia generating bacteria to develop within the bedding, that 
allowed us to obtain enough data to assess this time dependent process. 
4. 1.2.2 Mice and Husbandry Practices 
Outbred mice (female, HSD-ICR, initial age of 4 weeks see figure 4.32) were placed in the 
shoebox cages for a 13-day period. The bedding type was hardwood (Beta chip) shavings. The 
cages and accessories were washed and sanitized prior to use using standard procedures for 
laboratory animal facilities. The number of mice per cage was the maximum allowable for the 
mouse weight and cage area (five mice/cage). The cages were housed in environmental chambers 
when not in the calorimeters. The environmental chambers and the chamber that the calorimeters 
were kept in were all approved for housing laboratory animals and were ventilated at 10-15 air 
changes per hour (ACH). The light period was 12 h light and 12 h dark; lights were turned on at 
1:00 a.m. and off at 1:00 p.m. A white light and a blue light were on during the light period and 
only the blue light was on during the dark period. The light intensities of the light period and the 
dark period are presented in table 4. 1 .02. The mice received standard rodent diet and water ad 
libitum. 
Table 4.1.03 Light intensities in mouse facilities 
Calorimeter and Chamber 
White and Blue Light On 
Light Intensities (lux) 
White Light Off, Blue Light On 
Light Intensities (lux) 
Calorimeter 1 
10 
1 
Calorimeter 2 
42 
6 
Calorimeter 3 
10 
1 
Environmental Chamber #1 
Top 
Middle 
Bottom 
Top 
Middle 
Bottom 
(RH 35 percent) 
Shelf 
Shelf 
Shelf 
Shelf 
Shelf 
Shelf 
25 
7 
6 
2 
1 
1 
Environmental Chamber #2 
Top 
Middle 
Bottom 
Top 
Middle 
Bottom 
(RH 75 percent) 
Shelf 
Shelf 
Shelf 
Shelf 
Shelf 
Shelf 
16 
5 
4 
2 
1 
1 
The first three days after the mice arrived served as an acclimation period to allow the mice to 
adjust to their new surroundings and cage mates. The cages were kept at static conditions on 
