Pour petrol and leave it
When the entrance has been blocked and all the other openings have been sealed, petrol should be poured over the top bars of the top box to kill the bees. Usually 500 ml of petrol is sufficient for a 1-2 storey hive, while about one litre will be required for larger, 3-4 storey hives.
The petrol should be poured over the top bars as quickly as possible, with care taken to put the lid back firmly on the hive so that bees do not escape. The hive should then be left undisturbed for 10-15 minutes while the petrol vapour kills any bees not contacted by the petrol.
It is important to remember that the petrol is put into the hive to kill the bees, not as a fire accelerant. Petrol should not be used to douse the hive before burning. There is sufficient wax in the combs to fuel the fire.