NIOSH Report Identifies Factors Affecting Performance of Environmental Enclosures
A new report from NIOSH compiles the results of the agency’s research on environmental enclosures such as cabs on vehicles used in the mining industry to control workers’ exposures to airborne contaminants. These enclosures typically incorporate air filtration into their heating, ventilation, and air-conditioning systems. NIOSH cooperated with companies using environmental enclosures and with manufacturers of HVAC systems, cab filtration and pressurization components, and industrial vehicles to produce much of the research described in the report. The report provides key design guidelines for environmental enclosures, describes the measurement methods used for quantifying enclosure performance, and demonstrates mathematical modeling of filtration system designs.  According to the report, key factors that affect an enclosure’s effectiveness include using a separate intake pressurizer fan and a high-efficiency respirable dust filter to supply intake air into the enclosure; ensuring good enclosure integrity to achieve positive pressurization against outside wind penetration and to minimize outside air leakage around the filtration system; providing effective respirable dust filtration on the enclosure’s recirculated airflow; and applying secondary enclosure design considerations for maintaining an effective filtration and pressurization system. The report is available from the NIOSH website.