Fly Killing Machines

A UV or LED tube draws flies and other flying insects towards the unit, where they contact an electrified grid that kills them on contact. They run continuously, so they suit places flies keep arriving rather than a one-off problem.

Electric fly killers are made for use in occupied spaces. Site the unit out of reach, away from food preparation surfaces, and where the cable is not a trip or chew hazard. Follow the manufacturer's instructions for cleaning and for anywhere food is handled.

Away from competing light, since a unit next to a bright window draws far less than one on a shaded wall. Site it where flies gather - near a door, a bin, or the route in - rather than where you sit, and at the height the manufacturer specifies. Keep it away from food preparation surfaces.

They start catching as soon as they are running, though it usually takes a day or two before the difference is obvious. Running the unit continuously matters more than positioning it perfectly, because flies arrive in waves rather than all at once.

Usually light or siting. UV output falls over time even while the tube still lights, so an old tube draws far less than a new one - replace it on the manufacturer's schedule rather than waiting for it to fail. Beyond that, check it is not competing with a bright window and that it sits near where flies actually congregate. Clean out the tray as well, since a build-up of dead insects reduces what the unit catches.

The unit is working and the numbers are larger than it can keep up with, which means a breeding source or an open route in. Look for unsealed bins, blocked drains, standing water, compost near the house, or something dead in a loft or cavity. Fitting fly screens to windows and doors deals with the route in.

Switch the unit off at the mains, then empty and wipe out the collection tray - a build-up reduces performance and starts to smell. Replace the UV tube on the manufacturer's schedule and check the grid is clear of debris.