Vacuuming Asbestos Fireproofing Debris from Ceiling Tiles

Abstract

Many multistory buildings built in the 1950s through the 1970s have spray-applied asbestos fireproofing on steel and concrete decking supporting each floor. Typically this material is located above a suspended ceiling, which in many cases acts as a return air plenum for the heating, ventilation, and air-conditioning system. Performing mechanical work in this space often exposes workers to asbestos fibers if debris on the tops of the ceiling tiles is disturbed by the action of opening the tile ceiling or working in the space. This study investigated work methods to clean fireproofing debris inside an occupied building. Engineering controls including containment and high efficiency particulate air filtration vacuuming were used. Air samples were collected (1) on personnel, (2) in the area below the ceiling plenum, (3) as clearance samples in the plenum when work was finished, and (4) in ambient air during the day in other parts of the building sharing a common ventilation system. These samples were analyzed by phase contrast microscopy (PCM). Two of the highest fiber count personnel samples and three of the highest count ambient air samples were analyzed by transmission electron microscopy to gather information on fibrous glass content and asbestos fiber size distribution. The results showed asbestos fiber concentrations to be very low for workers and to have an insignificant impact on other occupied areas of the building. Most of the fibers counted by PCM were fibrous glass and cellulose, presumably from chafing the edges of ceiling tile when they were removed. In conclusion, the tops of ceiling tiles can be safely vacuumed in an occupied building if careful work practices and engineering controls are used and monitored.