Having read about the possible dangers of asbestos in WW2 gas mask filters, we decided it was time they were decontaminated to make them safe.
In fact, provided the filter is in reasonable condition, it should be perfectly safe. In service-issue gas masks (as opposed to the civilian-issue) there is a fibrous material resembling cotton wool in a number of layers, each layer sandwiched between two perforated metal plates.. Then there is a thick layer of activated charcoal chippings, sandwiched under pressure between two heavy-duty mesh barriers, with fabric and cotton wool to strain out any particles.
However, the argument is that given the fact that we do not know what has happened to it in the last 70 years, it could have got wet, and the barriers could have rusted through and be about to disintegrate.
So the bottom of the can was de-soldered and the plates and fibre removed, using a soapy spray on the fibre before starting to make sure that there were no airborne particles. Next, the charcoal was removed, and the inside of the can carefully inspected for stray fibres. To make absolutely certain that no fibre could possibly escape, the insides of all the cans were then coated in varnish, which was liberally applied, and poured out ensuring that any remaining particles are fully encapsulated. The base was soldered back on, and the can repainted.
Two cans were treated differently. One was in such nice original condition that we decided not to damage it, but to seal any fibres permanently inside. This was done by pouring a large quantity of epoxy resin into the side air vents of the can, and ensuring that it covered all of the inside areas. Any fibres would then be trapped in.
The final one was decontaminated as above, but the perforated plates were also decontaminated and varnished. The can was then carefully re-assembled using cotton wool with layers of different lengths, to show the can in section so we can see its construction.
Civilian-issue cans cannot easily be dismantled, so these were sealed with epoxy resin.
We have a certificate from an asbestos contractor for the safe disposal. We can now, hand on heart, say that all our gas masks are safe.