Fumigant dissipation rate

II. Toxic dose. Methyl bromide is threefold heavier than air and may accumulate in low-lying areas, and it may seep via piping or conduits from fumigated buildings into adjacent structures. It may condense to a liquid at cold temperatures (38.5°F or 3.6°C) and then vaporize when temperatures rise. Methyl bromide gas lacks warning properties, so the lacrimator chloropicrin (2%) is usually added. However, chloropicrin has a different vapor pressure and may dissipate at a different rate, limiting its warning properties. 

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