Phosgene odor threshold

Phosgene is a colorless vapor with a boiling point of 46.8°F. Thus it is normally stored as a liquid in a container under pressure above its normal boiling point temperature. The TLV for phosgene is 0.1 ppm, and its odor threshold is 0.5-1 ppm, well above the TLV. 

Phosgene is a colorless gas at ambient temperature and pressure. Its odor has been described as similar to new-mown hay (Leonardos et al. 1968). This mild odor and the weak acute irritant properties, however, provide little warning of its presence (Lipsett et al. 1994). The odor threshold has been established between 0.5 and 1.5 ppm (2.06 and 6.18 mg/m3) (Lipsett et al. 1994). 

NIOSH (1976) performed two studies to determine the odor threshold of phosgene. In the first, 56 military personnel were exposed to phosgene at increasing concentrations until all subjects could detect odor. The lowest detectable concentration was 0.4 ppm. Thirty-nine percent of subjects could detect odor at 1.2 ppm, and 50% of subjects detected odor at 1.5 ppm. In the other study, four subjects identified 1.0 ppm as the lowest concentration at which the distinctive new-mown hay odor of phosgene could be detected. 

Brownish to white monoclinic prisms, crystalline solid or powder with a phosgene-like odor (technical grade). An odor threshold concentration of 88 pg/kg was reported by Sigworth (1964). 

At ambient temperature and pressure, phosgene is a colorless gas which exhibits an irritating and suffocating odor. At low concentrations, it has a characteristic odor like moldy hay. However, the odor threshold of phosgene is higher than its toxic limit and one must remember that the sense of smell fails to detect small concentrations in air. 

Phosgene (military designation, CG) appears at usual battlefield temperatures as a white cloud whose density is due, in part, to hydrolysis. The gas is heavier than air and at low concentrations has a characteristic odor of newly mown hay. At higher concentrations, a more acrid, pungent odor may be noted. An odor threshold of 1.5 ppm has been reported but does not apply to all observers. This odor threshold is inadequate to protect against toxic inhalant exposures to this substance. Furthermore, a... 

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