Choosing a Diffuser for the Room You Actually Use

The most common mistake when buying a diffuser is matching it to a wish rather than a room. A 100 ml unit is right for a bedside table. It is not going to do much in an open-plan living room, and running it flat out will only shorten its life.

Match tank size to floor area

As a rough working rule, small tanks in the 100–200 ml range suit a bedroom, study or bathroom. The 300–500 ml units are the ones that make sense for a living room or a room where a door is usually open. Bigger tanks also mean fewer refills, which matters more than people expect once the novelty wears off.

Run time is the number to read

Makers list tank size prominently and run time in the small print, but run time is what you actually experience. A 300 ml unit on intermittent mode will usually outlast a 500 ml unit running continuously. If a listing gives both continuous and intermittent figures, that is a good sign the specification is honest.

Think about where it will sit

Ultrasonic units release a fine cool mist, so keep them off polished wood and away from anything that should not get slightly damp. A shelf at waist height, away from a wall, spreads scent better than a corner on the floor.