Odor threshold, formaldehyde

HVAC Materials Ventilation duct liners also react with ozone forming formaldehyde, acetone and C5—Ci0 aldehydes. Morrison et al. (1998) subjected new and used duct liners, air filters, sealants, sheet metal and other HVAC materials to ozone in small chambers. They observed secondary emissions of C5—Ci0 aldehydes from a new duct liner, a neoprene gasket and duct sealants. They predicted that secondary emissions from these materials could increase indoor aldehyde concentrations to levels comparable with odor thresholds. As will be discussed later, soiled HVAC materials also generate secondary products. 

The most common human response to formaldehyde vapor is eye blinking, eye irritation, and respiratory discomfort, along with registration of the pungent odor (10). The threshold for registration of formaldehyde stron y differs among people, and its impact depends on many factors. Thus, some poeple become accustomed to what they may consider the natural odor of "wood", while others become increasingly sensitized (29). The absolute odor threshold is... 

If acetal resins are processed at temperatures substantially above those recommended for the particular grade, minor amounts of formaldehyde may be Hberated. Formaldehyde (qv) is a colorless, lacrimatory gas with a pungent odor and is intensely irritating to mucous membranes. The human nose is sensitive to concentrations in the range of 0.1 to 0.5 ppm. The current threshold limit value for formaldehyde is 1 ppm. 

The minimum amount of formaldehyde that can be detected by odor varies considerably between individuals and ranges from 0.1 to 1.0 ppm (0.12-1.2 mg/m ), close to the concentration at which minimal irritant effects are felt in the eyes and in the pulmonary airways (3). Thus, the fundamental toxicity of formaldehyde lies in primary irritation to the eyes, nose, and throat when the subject is exposed to concentrations in the range of 1-5 ppm. Concentrations above 2-5 ppm cause irritation of the pharynx, lungs, and eyes, and some erythema of vaporized areas of the skin, such as the face and neck. Acute exposure to concentrations of formaldehyde of the order of three times the maximum threshold of detection of the... 

However, the vapor pressure of formaldehyde in commercial formaldehyde, sold as 37 wt% aqueous solution, or as solid paraformaldehyde or UF concentrate, exceeds 1 Torr (1. Since the absolute threshold (15) of the pungent formaldehyde odor is 0.05 ppm, many people notice, and some are sensitive to, the presence of products that emit residual formaldehyde. 

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