Improving Laboratory Animal Environments
Figure 1. Convective calorimeter used to measure heat, moisture and ammonia production of mice
Background
Air quality within macro (room) and micro (cage) environments of laboratory animal facilities is essential for the health and welfare of humans and animals, and the integrity of the studies being conducted. It is well-known that biological response are influenced by the environment. Information on the influence of the physical environment on the animals' biological responses is needed to improve laboratory animal facility design and management. At the optimum environmental condition, not only does the laboratory animal experience a state of well-being, the researcher obtains reliable and repeatable experimental results from the animal.
While many thousands of square feet of animal research facilities are designed and constructed each year, inadequate information is available regarding ventilation rates and patterns required to maintain acceptable micro- and macroenvironment. A scientific basis is needed for selecting the ventilation rates of the macroenvironment and microenvironment and for designing effective ventilation systems for laboratory animal facilities. Design information is also needed for engineers to improve design, ensure air quality, and minimize energy cost.
Limited research has been concluded to determine macro- and microenvironment relationships in animal research facilities in regard to ventilation rates, room air distribution, supply relative humidity and temperature, and other factors required to maintain acceptable and uniform cage environments. Most research has focused only on room conditions.
Laboratory animal ventilation should balance air quality, animal comfort, and energy efficiency to provide cage environments that optimize animal welfare and research efficiency. Conditions that optimize animal welfare automatically tend to improve research efficiency because good conditions minimize unintended stress factors on the animals. Additionally, the laboratory animal ventilation system should provide a healthy and pleasant environment for researchers and animal caretakers.
Figure 2 Wind tunnel for studies on effects of airflow on cage conditions
Objectives
This project was a collaboration between the National Institutes of Health ( Office of Research Services, Division of Engineering Services) and the University of Illinois bioenvironmental Engineering Research Laboratory (BERL).
- The objective of this research was to determine which room ventilation
parameters ( room ventilation rate, diffuser type, diffuser location, number
of exhausts, exhaust location, cage density, changing station location,
changing station on/off, room size, cage rack arrangement, and room pressurization
) affect both room (macro) and cage (micro) environment for laboratory
animal research facilities.
In order to develop relationships between micro- and macroenvironmental
conditions and to better determine ventilation system designs that provide
appropriate micro- and macroenvironments, the following were done:
 | Conduct a study to determine typical mass generation rates of CO2, H2O, and NH3, and consumption of O2, with groups of mice in shoebox cages with bedding at different room air relative humidities using open-system calorimeters with precisely controlled fresh air exchange rates (Figure 1). |
| Create and measure various airflows within a known mouse cage to determine the boundary conditions for the computational fluid dynamics (CFD) analysis of the cage (Figure 2). Cage boundary conditions include resistance and coefficient of loss created by both the cage top and the surrounding edge on which the cage top sits. The tracer gas method was used. |
| Obtain data in an empty room as well as a room with racks, cages, and simulated animals to verify the accuracy of CFD. Room air velocity, temperature, and CO2 concentration patterns were used throughout the room for verification of CFD model predictions (Figure 3) |
| Utilize over 500 CFD simulations to establish a relationship between micro- and macroenvironments by changing room ventilation rate, diffuser type, diffuser location, number of exhausts, exhaust location, cage density, changing station location, changing station status (on/off), room size, cage rack arrangement, and room pressurization. The simulations' variations would determine the effect on both room (macro) and cage (micro) environments for laboratory animal research facilities (Figure 4). |
Figure 3 Computer controlled sensor positioning traverse for the room studies
