Breeding problems in ventilated racks are caused by high stress factors. As a result, breeding problems and low reproductive performance are inherent to individually ventilated caging system. Mechanical equipment such as fans and blowers produce noise at about 60 decibels. Constant noise production in that range is detrimental to pups rearing as it covers up sound communication in the cage. Also, blowers generate vibration on the rack and in the cage.
Constant vibration creates an unsafe and stressful microenvironment to cage occupants.
Noise and vibration in the cage disturb cage occupants and prevent safe breeding conditions. Air valves that pressurize ventilated cages, even at low velocity, produce a high turnover of dry air. The small size of the valve and its location create a stream of air that generates great air exchange rate but also high air velocity, drafts, and dead air spaces. Pressurization of the cage generates particles from the bedding in the cage and leakage of the cage's effluent into the animal room. For example, air at 20 0C and moving at only 60 fpm has a cooling effect of approximating 7 0C. Chilling and dehydration, especially of hairless strains and neonates, and suspension of particulates in the air have detrimental effects.