Electronic & Ultrasonic Insect Repellers

These are dual-action units. The ultrasonic setting emits sound above the range of human hearing into the room; the electromagnetic setting sends pulses through the house wiring instead, with an LED showing which is running. Pest-Stop describes the waves as causing auditory distress to crawling insects and rodents, discouraging their presence in the home. There is no poison and nothing to empty or clear up afterwards.

Use it as well. A repeller discourages pests from settling; it will not clear a problem that is already established indoors. Deal with what is inside first using insect control products, close the entry points with insect proofing, then run a repeller alongside those to make the space less appealing to the next arrivals.

Ultrasonic output goes into the room the unit is plugged into. The electromagnetic setting sends pulses through the building's electrical wiring instead, so a single unit can cover multiple rooms on the same circuit. Units are sold by the area they cover - one room, small house or large house - so check the coverage stated on the product page and choose to suit the space.

No. Ultrasonic sound does not pass through walls, closed doors or furniture, and carpets, curtains and upholstery absorb it. Plug the unit into an open part of the room with nothing in front of it, or switch to the electromagnetic setting where you need to reach beyond one room.

There is no active substance and no poison - the unit plugs in and runs on mains power, so there is nothing to touch or swallow, and Pest-Stop states its indoor repellers are harmless to pets, children and pregnant women. The exception is pet rodents and rabbits: hamsters, gerbils, guinea pigs, rabbits and chinchillas hear well into the ultrasonic range and may be distressed, so do not run one in a room where they are kept. Use as directed.

Work out which of two things you are seeing. If insects are still arriving from outside, the problem is physical and the answer is proofing - gaps around pipes, vents, air bricks and door frames. If they are already established and breeding indoors, a deterrent will not remove them and the harbourage itself has to be treated. Read our guide to knockdown, residual and IGR treatments to work out which type applies.

In the room with the problem, at socket height, with nothing solid in front of it - not behind a sofa, inside a cupboard or under a shelf. Leave it running continuously rather than switching it on and off, and keep it clear of soft furnishings that would absorb the sound.