Posted By Martin Devlin We have a paint booth used to spray various paints onto metal sectional buildings (Off site construction). At times the booth needs to be cleaned out. This means scraping a layer of hard paint and paint dust from the floor. Before my time in the company, this paint was simply dumped into the general skip for landfill disposal. I pointed out that this was hazardous waste and our hazardous waste disposal company advised that we put the paint waste into empty 2 tonne chemical bags that they supplied and they would collect it. However, the bags went on fire during the night a couple of days later thanks to combustion. I was then told that 'oh yes the skips used to go on fire in the middle of the night.' The only solution that I can think of is to put the said waste into a metal container (skip size) with a metal lid. Would this be sufficient to stop combustion? Has anyone else experienced this and come up with a solution? Many thanks

Posted By Paul Leadbetter Martin Was the combustion spontaneous or could it have been deliberate? While some paints can generate heat during curing (and in a confined space, the heat may build up enough to cause combustion), a dried paint film should surely have got passed that stage and be relatively innocuous. Paul

Posted By Robert. Definately wouldn't advise a sealed metal drum as a chem reaction may already have started. That could end up as a dangerous pressurised vessel without anyone realising. you may need to know what is causing the combustion. It could be that other non-compatible substances are being disposed of without you knowing.

Posted By steve e ashton If any of the paints are 'two pack' - isocyanate / epoxy / acrylate or simliar - then the 'curing process' will generate heat - I would be surprised, however, if this is still going on after the two pack components have been mixed, sprayed, settled on the floor, left for several days then scraped up and binned / bagged. If for some reason there is some 'unmixed' two-part component on the floor which is being 'mixed' as a result of the scraping together - then this could / might possibly provide a mechanism for the self- heating you seem to be describing. The heating normally occurs in very thin layers when sprayed, so the temperature doesn't go up much (convection and conduction), but mixed in bulk, the material can be self - insulating and may get very hot. Don't try to mix a full pack of araldite and enclosing the mixed paste in a small jar or tin.... (Then DON'T put your material into a sealed drum!) Incidentally, if you are spraying two part paints, you should be aware there may be very significant health hazards that could give you worse problems than the occasional skip fire! If you are NOT spraying two pack, then I would be looking for a source of pyrophoric materials - any precious metals (are you spraying gold or platinum compounds? (I worked at one plant that had an extremely large vent system fire due to finely divided osmium or rhodium settling in the ducts) or finely divided aluminium (powder coating...think thermite) - are you shot blasting before painting? or could it be spontaneous heating (oil-based paint mixed with sawdust?). Trying to guess the precise source of your problem without seeing the plant and knowing the (precise composition of) materials involved is very difficult - the only proper answer to your query at this stage is "It depends...." Steve

Posted By John A Wright Just some advice about cleaning spray booths. Next time you've got them scraped nice and clean, spray a special peelable coating all over the booths AND the overspray area. When cleaning time comes you just peel everything off. Using this process improves H&S and also means less frequent cleaning operations - you can let more build up. John W