Case studies of a spring grinding factory, one hard chrome plating shop, a welding operation, and a degreasing facility that recirculate exhaust air, and one hard chrome plating shop and a dry cleaning establishment that do not were reviewed to determine the validity of qualitative recommendations and analytical design procedures for the recirculation of industrial exhaust air. The methodology was retroactively applied to identify and evaluate how its use may have altered the design process, and additional application of the methodology to new recirculation systems for interested industrial establishments was studied. The model considered legal issues, energy consumption, contaminant classifications, air cleaner and monitor availabilities, process emission profiles, and ventilation system designs pertinent to each situation to determine feasibility. Methodological limitations and difficulties included retroactive assessments, sampling, tracer gas studies and facility access. The authors conclude that the recommended approach furnishes a framework for the design of recirculation systems and is of value in identifying and resolving problems of health and safety. They also propose potential resolutions to the limitations of this approach.
NIOSH, Division of Physical Sciences and Engineering, NIOSH, Cincinnati, Ohio