Unscented candles are the quickest way to change a room in winter (sample note).
Dinner candles burn for six to eight hours; a 7 cm pillar for about thirty. Trim the wick to 5 mm before you light it, and let a pillar burn until the whole top has melted the first time, so it does not tunnel.
Never leave a candle burning in an empty room, and keep it a hand’s width from anything that can catch.