Spray booths are a common sight in the industrial sector. Designed to remove pollutants during industrial processes such as spray painting or welding, a booth is a rectangular enclosure open on one side where the worker stands, and equipped on the opposite wall with a fan and filter arrangement to suck away the dirty air. The full-size mannequin in these photographs simulates a worker in a spray booth facing the exhaust filters. In experiments designed by LBL researcher Ashok Gadgil, smoke was released in front of the mannequin to simulate the spraying of paint in the booth.
The photo on the left shows the spray booth during standard operation. The smokeórepresenting a pollutantóis entrained in the eddy that forms in front of the mannequin, rising to the figureís breathing zone. The concentration of pollutant in the breathing zone of the mannequin was found to be about the same as the concentration at the exhaust chimney.
The photo on the right depicts the same experiment, except that the little box on the mannequin's chest is continuously ejecting a small amount of air, hence the name airvest. This arrangement, intended only as a proof-of-principle experiment, ventilates or eliminates the eddy in front of the worker, causing the smoke to jet away. The pollutant concentration at the breathing zone is reduced by 100- to 800-fold, depending on how much air is ejected from the box.
With the airvest, it appears possible to substantially reduce the fan speed in the spray booth and simultaneously reduce the workerís exposure to industrial pollutants. A reduction in spray-booth flow rate by a factor of two will result in significant energy savingsóon the order of $1,000 annually per shift per booth, depending on the local climateófrom reduced heating, cooling, and filtration of the incoming make-up air. This reduction in energy use accompanies a 50-fold reduction in the workerís exposure to pollutants generated in the booth.
LBL has acquired a patent and is discussing collaboration with a private-sector firm in California. The airvest technology still needs some developmental research to improve its ergonomics. Gadgil believes that research may also reduce its costs significantly below the current estimate of about $200 per unit. Field tests of the improved design must precede full commercialization.
Spray-booth exposures without the airvest (left); a higher booth velocity and no airvest (center); and the airvest on with the recommended lower booth velocity.*Hood velocity is measured in feet per minute (FPM). Airvest flow rate is measured in cubic feet per minute (CFM).
--Ashok Gadgil
Ashok Gadgil
Indoor Air Quality Controls Project
Indoor Environment Program
(510) 486-4651; (510) 486-6658 fax