hi all.found out recently a fact about CO other than its colourless and odourless.....and its deadly at first the lungs like it(absorbtion).then as it saturates the blood stream it eventually paralyses the person(s) the scary bit is that the brain knows that something is wrong but the body cant move!! also its accumulative( big word!) in that small doses mount up to so in my opinion check those flames,if the're yellow(sooty) get the fire checked out or the boiler checked.incidentally anybody got one of those CO detectors?not got one myself but will put on next shopping list