Adam Clarke on Psalms 18:8

There went up a smoke out of his nostrils - Or, 'There ascended into his nostrils a smoke,' as the words, literally rendered, signify. The ancients placed the seat of anger in the nose, or nostrils; because when the passions are warm and violent, it discovers itself by the heated vehement breath which proceeds from them. Hence the physiognomists considered open wide nostrils as a sign of an angry, fiery disposition. "This description of a smoke arising into and a fire breaking forth from the nostrils of God, denotes, by a poetical figure, the greatness of his anger and indignation. "Fire out of his mouth devoured - means that consuming fire issued out of his mouth. Coals were kind led by it, thus we render the next clause; but the words do not mean that fire proceeding from God kindled coals, but that burning coals issued from his mouth; and it should be rendered 'living coals from his mouth burned, and consumed around him.' - Chandler.