Suggest you scrap it. They were highly controversial at the time. The bloke then tried to claim that they should only be used for collapsing burrows empty of creatures. What ? Send in the ferrets first ? or poison gas. Or the olde fashioned way, connect in the exhaust pipe from say an old chain saw running a rich mix.
Never came to a test case, but here are a couple of links:
Natural England Notice | Rodenator
Defra Statement | Rodenator
The question is often “could the Rodenator and similar devices ever be used to kill pest species in England?” The simple answer is yes, but only under an appropriate licence as they utilise a prohibited method of killing. Natural England is authorised to grant such licences on behalf of Defra in England. The Welsh Assembly Government and the Scottish Government are responsible for this issue in their respective countries. To date, there have been discussions between Natural England and importers and purchasers to advise them of the regulatory requirements but no licences permitting the use of these devices to kill wild animals have been granted anywhere in the UK and no such devices are ‘Defra approved’.
There again, blowing a (hopefully) stochiometric mix of propane and air, or even propane and oxygen even better, somehow expecting it to blow through all the burrows and chambers displacing all the plain air, then the detonation wave propagate throughout is a big ask.
Undoubtedly they went bang and collapsed some things. Being a bit safety conscious I would not like to try to operate one.