Air fresheners emit fragrance to mask odour, although you can also find products that oxidise, absorb or sanitise sources of odour. Air fresheners come in two main varieties. Instant action products such as sprays and atomisers are activated by the user when needed, while continuous action products such as wall plug-ins produce an ongoing defence against unwanted smells.
Spray air fresheners release a liquid that dissolves in the air. They release fragrance molecules that freshen up a room and make it smell pleasant. You can also buy plug-in air fresheners that automatically release a burst of fragrance molecules into the air at timed intervals or when motion is detected.