Hi Boo, how goes it!! If you have a gas fire turn off the pilot before you do any dusting with any powder! any powder can cause a dust explosion. You neen to go to your hardware store and by any ant powder that contains Benciocarb, get loads of it under and around your fire, you really need to work at this, a bit of haphazard sprinkling will not do the trick!!! and can be difficult to get rid of at the best of time, you need to get it in all the little nooks and crannies, you could also mix a bit of sugar with some of the powder in a bowl to tempt the little terrors, try and keep pets away but at the end of the day they would need to consume vast amounts of the stuff to harm them. I stress you need to be thourough to rid these little blighters and you may well get them back each year in the same place. Happy hunting :!!!!