能源成本的增加迫使工业界开发出减少与通用和局部通风设备相关的热损失的方法。这必须以确保空气污染物水平保持在安全水平的方式进行。使用间接热交换器可将污染物重新引入工作区域的可能性降至最低，但这些交换器效率相对较低，需要安装和维护大量设备。直接将工艺空气重新引入工作区域对于热回收来说是非常高效的，但除非对空气进行充分处理并采取适当的保护措施，否则空气污染水平可能会过高。再循环正在工业环境中使用，其结果既有可预测的，也有不可预测的。本文介绍了几个案例研究，其中废气再循环的应用取得了不同程度的成功。 讨论涉及许多不同的情况和行业。它强调了工业卫生学家的观点。案例研究包括以下情况:铸造厂的有效粉尘控制对控制同一操作期间发生的一氧化碳暴露几乎没有作用。在一家机械车间，油雾由局部排气和整体通风控制。空气清洁是用静电除尘器进行的。这台设备能产生臭氧。焊接操作的局部排气通风控制金属烟雾，几乎不考虑其他污染物。一家天花板材料制造商有意设计了一个通风系统，其中一种污染物通过再循环空气控制，而其他污染物则排放到室外。 在电子行业，手工焊接产生的烟雾被从操作员的呼吸区清除，以便在另一个区域进行一般空气稀释。这种做法影响了另一名工人所在区域的污染物浓度。在每一种情况下，本文描述了所采用的控制措施所涉及的行业或过程，并讨论了预期和实际结果。如果所选解决方案的替代方案可用，也将对其进行说明。引文:研讨会论文，佐治亚州亚特兰大，1984年

Increased energy costs have forced industry to develop ways to reduce heat losses associated with general and local ventilating equipment. This must be done in a manner such that air contaminant levels are maintained at safe levels. The use of indirect heat exchangers minimizes reintroduction of contaminants into the work area, but these exchangers are relatively inefficient and require the installation and maintenance of a great deal of equipment. Reintroduction of process air directly into the work area is highly efficient for heat recovery, but unless the air is adequately treated and there are adequate safeguards, air contaminant levels may become excessive. Recirculation is being used in the industrial environment, with both predicted and unpredicted results. This paper presents several case studies where the use of recirculation of exhaust air was applied with varying degrees of success.The discussion involves a number of widely varying situations and industries. It emphasizes the point of view of the industrial hygienist. The case studies include the following situations:Effective dust control in a foundry did little to control carbon monoxide exposure occurring during the same operations.In a machine shop, oil mist was being controlled by local exhaust and general ventilation. Air cleaning was done with electrostatic precipitators. This equipment is capable of generating ozone.Local exhaust ventilation for a welding operation controlled metal fumes with little regard for other contaminants.A ceiling material manufacturer intentionally designed a ventilating system whereby one contaminant was controlled by recirculating air while other contaminants were exhausted to the outside.In the electronics industry, smoke from hand soldering was removed from the operator's breathing zone for general air dilution in another area. This practice affected contaminant concentrations in another worker's area.In each of these cases, the paper describes the industry or process involved control measure applied and the desired and actual results are also discussed. If alternatives to the chosen solution were available, these are also described.