在实验动物的物理环境中，圈养或饲养系统是最重要的单一要素之一。已经制定了评估此类系统的标准。除了使用层流原理的系统外，大多数笼子都是被动的，因为空气交换或通风是通过自然而非机械方式进行的。因此，笼子中的空气交换率与房间空气分布模式、空气交换率以及笼子中产生的热量和污染物量有关。动物设施的温度、湿度和通风率（表1）是在笼中保持相同环境条件的假设下规定的。 1954年，大陆和Herrera报告说，假设笼子和房间环境之间没有差异，这可能在统计学上是无效的，将实验治疗与笼子效应混淆可能会使实验无效。从那时起，其他报告已经确定了动物笼子和周围空间之间的热、气体和颗粒物浓度差异。由于没有数据可以确定与室内条件相关的空气交换率和笼子微环境的其他参数，我们开展了本文报告的工作。引用:ASHRAE交易，第81卷，第一部分，新泽西州大西洋城

The caging or housing system is one of the most important single elements in the physical environment of laboratory animals. Criteria have already been established to evaluate such systems. Except for systems that use laminar flow principles, most cages are passive because air exchange or ventilation occurs by natural rather than mechanical means. Thus, the air exchange rate in a cage is related to the room air distribution pattern, the air exchange rate, and the amount of heat and contaminants generated in the cage.Temperature, humidity and ventilation rates (Table 1) for animal facilities have been specified on the assumption that the same environmental conditions of a room are maintained in a cage. Mainland and Herrera reported in 1954 that it may be statistically invalid to assume no difference between cage and room environments and that confounding of experimental treatments with cage effects may invalidate an experiment. Since then, other reports have identified thermal, gaseous, and particulate concentration differences between animal cages and the surrounding space.Because no data exist to determine air exchange rates and other parameters of cage microenvironments relative to room conditions, we undertook the work reported here.