My gas boiler is wall fitted and is set up in my kitchen close to my sink. The housing association has done a half arsed job and the flue has yellow expansive foam coming out of it with no cover over it. I was putting lining paper up in my kitchen ready to be painted. I was trimming the lining paper around the flue area with a stanly knife and as i was doing so there was a loud bang and sparks. It has tripped one of my fuses in the fuse box. Im a little scared to put it back on. Can someone please help explain whats happened here? The stanly blade has black on the blade. I think i was lucky. Whatever i did i think it may have been fatal if i hasn't moved away so quick with the blade. I don't understand tho how the foam could make that effect. I wasnt cutting anywhere near a plug or around sockets. Just near this foam stuff around the boiler.