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0.3 ppm. In controlled chamber studies, individuals begin to
sense eye irritation at about 0.5 ppm; 5 to 20% report eye
irritation at 0.5 to 1 ppm; and greater certainty for sensory
irritation occurred at 1 ppm and above. While some agencies
have used a level as low as 0.1 ppm as a threshold for
irritation, the expert panel found that a level of 0.3 ppm would
protect against nearly all irritation. In fact, the expert panel
found that a level of 1.0 ppm would avoid eye irritation—the
most sensitive endpoint—in 75 to 95% of all people exposed.
Formaldehyde emits from a variety of construction materials,
furnishings, and consumer products. The three products that
emit the highest concentrations are medium-density
fiberboard, hardwood plywood, and particle board.
Environmental factors such as temperature and relative
humidity can elevate levels because formaldehyde has a high
vapor pressure. Formaldehyde levels from building materials
are the highest when a building first opens because materials
have had less time to off-gas. Formaldehyde levels decrease
over time as the sources suppress.
A Guide to Formaldehyde Exposure Levels
0.03 ppm
0.10 ppm
0.40 ppm
0.50 ppm
6
Average outdoor level
Recommend upper short-term exposure
limit (STEL) limit for residences by ASHRAE,
ANSI, EPA, and NIOSH
Recommended upper STEL for
manufactured homes
OSHA's workplace limit
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