When people think about the hazards of a thermal fogger, they think of the hot barrel or the chemicals. There is another risk that is almost always overlooked: fuel left standing in the tank.

A fogger's fuel tank is closed by a cap with a rubber seal. When that seal degrades through heat, chemicals and age, fuel vapour escapes continuously, even while the machine sits idle.

This article tells the true story of a kindergarten that found fuel vapour accumulating in a store room adjoining the corridor to its classrooms, and explains why this matters and how to prevent it.