鉴于目前对环境保护和工业安全的重视，来自附近排气口的进气污染问题近年来变得越来越重要。此外，通过再生热交换器从排气中回收能量目前是医疗设施的常见做法，随着燃料成本的持续上升，这种形式的能量回收在其他情况下也可能变得经济合理。进气和排气都需要通过一个热交换器，这可能导致进气和排气口位置之间的间隔缩短，而这反过来只会加剧进气污染问题。

The problem of air intake contamination from nearby exhaust vents has developed increasing importance in recent years in light of the emphasis now placed on environmental protection and industrial safety. Also, energy recovery from exhaust air by regenerative heat exchangers is presently a common practice for medical facilities, and as fuel costs continue to rise it is probable that this form of energy recovery will become economically justifiable in other situations as well. The need for passing both inlet and exhaust air through a single heat exchanger can dictate a shorter separation between inlet and exhaust vent locations, and this in turn can only serve to aggravate inlet air contamination problems.