Use of tracer gas techniques for industrial exhaust hood efficiency evaluation - application of sulfur hexafluoride for hood controlling particulate emissions.
Am Ind Hyg Assoc J 1985 Jul; 46(7):379-386
The relationship between hood particle capture efficiency and hood efficiency as determined by tracer gas techniques was investigated. A particulate tracer and sulfur-hexafluoride (2551624) (SF6) were compared. Tracers were released continuously from the blood duct inlet and at various locations around the hood. Tracers were simultaneously discharged normally and horizontally toward the hood air flow at various discharge velocities and locations to obtain velocity ratios. Laboratory and field studies were compared. A mathematical model of the relationship between efficiency and velocity ratio was derived. Efficiency was similar for the two methods. Efficiencies of larger particles decreased with increasing velocity ratio. At velocity ratios larger than 5.8, SF6 efficiency decreased with increasing velocity ratios faster than that of any sized particles. In the field, the SF6 efficiency was not as high as laboratory values. The equations were not valid when the contamination discharge and hood velocities approached that of the surrounding air velocity. The authors conclude that for hoods controlling particles of 3 micrometers in diameter no correction of hood efficiency data estimated by the SF6 technique is needed. For larger particles a correction factor should be used.
NIOSH-Author; Industrial-hygiene; Pulmonary-clearance; Air-monitoring; Respiration; Air-sampling; Lung; Analytical-models; Exposure-methods; Pulmonary-disorders; Breathing-zone
American Industrial Hygiene Association Journal