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Ventilation Design Handbook on Animal Research Facilities Using Static Microisolators 
The cage also contained one of two mouse heater representations: a simple, small electric heater, 
that will be known hereafter as the default mouse heater (DMH) (shown in figure 4.12); and a 
more realistic representation of the physical presence and heat transfer characteristics of the mice 
huddle, that will be know hereafter as the simulated mouse object (SMO) (shown in figure 4.13). 
In the cases that included the DMH, the cage had an electric heater placed on the bedding 
towards the front of the cage that produced heat equivalent to the total heat production of five 
mice weighing 2.0e-2 kg (4.4e-l lb) each, 2.3 W. Heat production simulated was based on the 
ASHRAE (1993) equation: 
ATHG = 2.5 M (4.1) 
M = 3.5 W 0 - 75 
Where: 
ATHG = average total heat production from laboratory animal, W/animal 
M = metabolic rate of animal, W/animal 
W = mass of animals, kg 
The DMH was a 200 ohm precision resistor with approximately 21.5 V of direct current from a 
regulated, filtered D.C. power supply. 
In the cases that included the SMO, the cages included a more accurate mice huddle 
representation, that was placed within the cage at a location centered width-wise and towards the 
front one-third in the same location as the resistor heater (see figures 4.08 to 4.10). The SMO 
was designed to simulate five mice for volume obstruction, sensible heat production, and surface 
temperature. The mice were simulated using 2.20e-lm (7/8") outside diameter PVC pipe. The 
pipe had a wall thickness of 2.4e-3m (3/32") and was cut to 4.3e-2m (1-11/16") lengths. The 
ends of the pipe were covered with duct tape and plastic caps (see figures 4.13 and 4.14). 
Sensible heat was simulated using one 200 ohm precision resistor powered at 9 volts per pipe. 
Before starting the experiment the surface temperature of the SMO was measured several times 
at various locations, using a Cole Palmer infrared thermometer (see figure 4.14), and shown to 
closely correspond to those found on the fur of the dorsal surface of mice by Chris Gordon 
(about 26.7 °C (80.0 °F)). Justification for the physical sizing of the SMO is given in appendix I: 
section 2.3. 
In both mouse heater representations, a voltage regulator (Epsco model EFB) was used to 
produce the voltage. The voltage was constantly monitored using a Fluke 75 multi-meter. 
Resistance was checked at the beginning of each experiment with the Fluke to guarantee the 
resistor was in working order. 
The cage was instrumented to measure air velocities approaching or moving past the cage on all 
four sides, at approximately the top edge of the cage, or the lip of the top. An air velocity sensor 
was placed on each of the four sides at approximately 2.0e-2m (0.75") distance out from the cage 
at the midlength of each side. Air velocities, temperatures, and air exchange rates were measured 
