Abstract
To determine how a filter cap affects the heat and moisture build-up in a mouse cage, and how that build-up is affected by ambient conditions of temperature and relative humidity, 50 adult female mice were housed 10 per cage in polycarbonate cages, which were covered with a fibrous filter and sealed with a neoprene gasket and hold-down rod. The cages were placed in a chamber which controlled ambient temperature and humidity. Observations were made at 1°F intervals of temperature (68–74°F, 19.9–23.3°C) and at three different relative humidities (40, 55, and 70 per cent). Every 24 hours the chamber conditions were changed, and cages, bedding, water, filter caps, and food were replaced. Three sensors suspended just under the filter cover measured temperature and humidity and transmitted the data to a recorder. The first reading was taken after a 3-hour equilibraiion period, then every 3 hours until the next day's change. By measuring the average temperature and humidity, it was possible to study the differences between cage and ambient conditions. At 68°F (19.9°C) and 40 per cent relative humidity, the mean conditions in the cages were 72°F (22.2°C) and 50 per cent; at the upper limit of 74°F (23.3 °C) and 70 per cent, the mean cage conditions were 78°F (25.5°C) and 75 per cent.