Bromomethane, commonly known as methyl bromide, has been used as a general wide-ranging pesticide for years. It is not specific to any type of bug but gets them all; unfortunately it is also toxic to humans and an ozone depleter. Because of this it has been included in the list of substances the use of which is to be banned under the Montreal protocol. Nevertheless it is still being used by a number of countries particularly on exports of plant based products. We came across it when our inspectors had to deal with tree ferns being imported from Australia. One issue we had was that it was very difficult to work out exactly how much of the stuff was left in the container after it had been fumigated. The reason it is so popular as a fumigant is that it is extremely volatile so in theory after it had done its fumigating bit it just goes up into the atmosphere. Shipping containers are not the most airtight of objects and so the fumigant should have a chance to disperse as the goods travel across from the Far East (takes about two weeks at least). But it might be possible for some of the fumigant to be absorbed by things like packing materials and (in our case the trunks of tree ferns). We arranged for the port staff to check for methyl bromide before any of our staff were allowed near the container. I can’t remember if they used Drager tubes or some other type of detector. Phosphine is also a volatile fumigant which is toxic to humans. Unlike methyl bromide it is not banned under the Montreal protocol as it is not an ozone depleter. Like methyl bromide it is very volatile and should not leave any residue but again it might be absorbed by packing material for example. The commercially bought stuff has strong garlicky smell. Phosphine should not be confused with phosgene which is a chemical warfare agent.