The term FIREPLACE POWDER can be broken down into two words, with the first word being 'ASH' which is a 3 letter word. ASH is a residue that is left behind after something has been burned or destroyed. Fireplace powder is a type of fire extinguishing agent that is used to put out fires in fireplaces and other enclosed spaces. It is made up of a combination of chemicals that work together to smother the fire and prevent it from spreading.