Phosphine Detection

Phosphine Detection

Phosphine

Phosphine is the common name for phosphorus trihydride (PH3), also known as phosphane and, occasionally, phosphamine. It is a colourless, flammable gas with a boiling point of -88°C at standard pressure.
 
Pure phosphine is odourless, but technical grade phosphine has a highly unpleasant odour like garlic or rotting fish due to the presence of substituted Phosphine and Diphosphine (P2H4). Phosphine is highly toxic and deadly at low concentrations. Because of this, the gas is used for pest control by fumigation.
 
Phosphine is also used as a dopant in the semiconductor industry and a precursor for the deposition of compound semiconductors. Recently, high purity tertiary butyl phosphine (TBP) has been developed as a less hazardous liquid alternative to highly toxic phosphine gas for application in Metalorganic Vapor Phase Epitaxy (MOVPE) of III-V compound semiconductors.
 
Phospine Characteristics
Synonyms Phosphorous trihydride, Hydrogen phosphide
CAS No. 7803-51-2
Chemical formula PH3
Vapour density 1.18 (air = 1)
Safe Work Australia ES TWA 0.3 ppm
STEL 1 ppm
Flammable limits LEL 1.79% by volume
(ref: http://www.cdc.gov/niosh/npg/npgd0505.html)
UEL  
Equipment group ---
Temperature classification ---
Chemical/physical properties At room temperature, phosphine is a colourless gas. Although odourless in its pure form, impurities present when it is formed under natural conditions give it an unpleasant garlic-like or rotting fish odour. This odour is detectable by smell at around 0.5 ppm. 
Phosphine is flammable with an ignition temperature between 40–65°C, but may ignite spontaneously at room temperature due to impurities.
Hazardous properties If inhaled, phosphine is a severe respiratory irritant, with prolonged exposure leading to breathing difficulties, pulmonary oedema and possible effects on the gastrointestinal and central nervous systems.  
Occurrence/Uses Phosphine is used extensively to fumigate grain, food products and tobacco. It is produced by the action of atmospheric humidity on pellets of aluminium phosphide.
It is also used as a doping agent in semiconductor production.
Detectors available Electrochemical (0–5 ppm and 0–1,000 ppm)
Gas detector tube (0.05–6,000 ppm)
Colorimetric paper tape (0–1,500 ppb)
Suggested alarm levels Lo: 0.3 ppm
Hi: 1 ppm
Notes