Dangerous concentrations of methyl bromide used as a fumigant in Belgian greenhouses.

In the disinfection of soil in greenhouses, methyl bromide can be applied to the soil by injection or by fumigation on the surface. The concentrations of methyl bromide in the air are measured, and the differences between each technique discussed. Concentrations during injection vary between 100 and 1,000 ppm with peaks up to 3,000 (10,000 in one case) ppm, but drop below 200 ppm if preventive measures are taken. During fumigation concentrations remain between 100 and 1,000 ppm. Large variations occur within a technique depending on the quality both of the material and operator.