Fumigation

In the 50s, there were fewer owner occupied homes in the UK than there are nowadays. Maybe there were more rented properties changing hands. For whatever reason, I have a memory of seeing several houses being fumigated whereas I do not recall seeing one being done in the last 30 years. Great sheets of canvass (? maybe something else, perhaps rubber) were carefully placed all over the house and fumigating gas or smoke was released inside the house; the cover was to stop the poisonous gases from killing the neighbours although I have no idea how they managed it in a semi-detached or terraced house. The covers were left on for several days (I watched the process on different houses as I walked or ran to school). I suppose that pests of any type were eradicated.