Why risk it,take it to a recycling center to be made into mulch.some old treated wood has poisonous chemicals to the touch so I would say it is poisonous to breath...the newer treated wood has been treated with a copper mixture which I believe is not dangerous to touch but same as the other no smoke from treated wood or any wood is good to breath..and not to mention fire codes in your area to prevent burning down your house or a neighbors house or property...you know the forestry commercials with the bear(smokey that is)...