Cool Your Coals! Email Do not put hot coals or ashes in your carts! Hot ashes or coals can cause severe burns and fire damage to properties. Follow these safety measures when disposing of them: Use metal cans no more than 30 gallons in size with tight-fitting metal lids. Fill cans with hot ashes only halfway so they cool quickly and are light in weight. Secure metal lids on cans to prevent spread of sparks or embers. Check, stir, and water your ash cans for several days until completely cool. Avoid adding more hot coals on top of the cool coals by using a set of cans that can be used sequentially. Check to be sure that ashes are completely cool before placing them in your compost cart.