What to do if…
you find a large insect swarm indoors and suspect a nest in the building

What to do now

1. Create a safer pause. Move calmly to a room away from the swarm, close the door, and keep pets with you. If you can do it without going near the insects, put a towel or draught excluder at the bottom of the door.
2. Check for an emergency medical situation. If anyone has swelling of the lips, mouth, throat or tongue, is wheezing, struggling to breathe, faint, very dizzy, confused, drowsy, or has collapsed after a sting, call 999 and say you think it may be anaphylaxis. If they have been prescribed an adrenaline auto-injector and it is available, follow the instructions on the device. Keep them still; they should not stand or walk around.
3. Reduce movement routes only from safety. If a fan, extractor, or heating and ventilation control is safely reachable without approaching the insects, switch it off for now. Leave any controls that require you to enter the affected area.
4. Contain the affected room. Keep internal doors closed. Only open an external window in that room if you can do it without going near the cluster, nest point, or flight path.
5. Record what you can from a distance. If safe, take a zoomed photo or short video. Note whether insects are clustering at a window, light fitting, vent, chimney breast, skirting, ceiling, or a single wall or roof point.
6. Look for a single entry or exit point without approaching it. Repeated movement through one crack, vent, chimney, soffit, ceiling gap, or light fitting can suggest a nest or colony in the structure.
7. Arrange appropriate help. Contact your local council to ask whether they offer pest-control services or advice. If you suspect wasps, hornets, or you are unsure what the insects are, contact a professional pest controller and say this is an indoor swarm with a possible nest in the structure.
8. If they may be honey bees, use bee-specific help. A local beekeeping organisation may be able to advise on swarms. If honey bees are established inside the fabric of the building, specialist removal may be needed rather than ordinary swarm collection.
9. If you are in a flat or shared building, tell the building manager, freeholder, factor, or managing agent promptly. A nest in a roof, wall, chimney, or service void may affect more than one home or a communal area.
10. If you rent, tell your landlord or letting agent promptly in writing. Ask who is arranging pest-control advice and what you should do meanwhile. If the situation is not being dealt with and you think the home is unsafe, ask your local council for advice.