Assume Nothing

The building was constructed as a large automotive garage, capable of serving eight large trucks, with adjoining two-story offices, showers, and locker rooms. The offices, showers, and locker rooms were separated from two-story-high truck bays by a fire-rated concrete masonry wall. Conditioned air was provided by a number of package-terminal-air-conditioning (PTAC) heat-pump units under the windows. Outside-air ventilation was provided through ceiling-mounted open grilles, presumably from vented ceiling plenums. The room exhaust was ducted from ceiling-mounted exhaust grilles up to roof-mounted exhaust fans.

The office occupants were running exhaust fans to no avail. Truck engines were run inside the garage without using hoses to exhaust to the outside. The indoor air was heavy with truck fumes, and the situation continued unabated.

When I poked my head above the ceiling tiles, I could see light coming through the rated partition wall. Truck exhaust was entering the ceiling plenum through where the wall was unsealed. Upon further investigation, I discovered that the original construction drawings had no fresh-air-intake design, yet the building was constructed and approved as such.

Operating exhaust fans only compounded the situation by drawing contaminated air into the conditioned space. To exhaust air, makeup air also is needed. However, there were no provisions for that. In fact, the makeup air was the odorous air entering the
ceiling plenum from the truck service area, which subsequently was drawn into the room through the open ceiling grilles before finally being exhausted.

To remedy the situation, I designed a roof-mounted air intake, specified sealing for the rated partition wall, and, because it was a high-visibility issue at the time, designed ceiling-mounted recirculating-air purifying systems.

The moral of the story: Do not assume that any building is designed and built correctly, even if it is new.

Edward Liwerant, PE
R.E. Lamb Inc.
Norristown, Pa.

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