The usage of Air curtain units, installed on the large openings of industrial buildings is one of the most practical and effective preventive methods applied against the uncontrolled outdoor cold air flows through the open doorways. The prevailing outdoor conditions and sometimes the indoor mechanical ventilation conditions do vary during the opening periods of the doorways of an industrial building.

The need for control of cobalt from saw filing has been demonstrated by health studies in Finland, Washington state and British Columbia. I am most familiar with the study done in BC, because that is where I live and work. That study was done by a team led by Drs. Susan Kennedy and Kay Teschke, of the University of BC. They observed work activity and measured filers lung function in 8 sawmills, from June to December 1991. They found a high incidence of significantly below normal lung function. Their report was widely and effectively communicated to the sawmill industry.

Upwards blowing air curtain includes usually a shaped inlet, a fan, an outlet duct, sound attenuators, an underground plenum and a nozzle. Warmed air or outdoor air is blown from the nozzle forming a jet which travels the width of the doorway and run into the upper edge of the doorway. Upwards blowing air curtains are normally used in doorways to protect workers and processes from cold outdoor air and to reduce energy and maintenance costs of the industrial buildings (1,3).