If you thought that the cleaner and more efficient outdoor furnaces are, the harder they are to operate, it’s time to think again. CleanFire outdoor furnaces are not only EPA Step 2 Certified, they are specifically engineered and designed to be easier to operate than ever before. High efficiency. Clean burning. Easy to operate. Easy to maintain. Built to last a lifetime. The CleanFire 300, 500 and 700 outdoor wood furnace is EPA Step 2 Certified.