Phorid flies breed in places with lots of moisture plus decaying material. Fix leaks, reduce humidity in basements and infra-spaces.
I had a bad infestation and what finally worked was: (1) sealing floor drains and crawlspaces, (2) treating the organic buildup in pipes with enzymatic cleaners. That removed the breeding site.
Using aerosol sprays helps knock down adults, but alone won’t solve the problem. You must remove the larval food source. Otherwise you’re just temporary.
@SanitationSally Good point. These flies can breed under slabs, inside wall voids near leaking pipes, places you might not suspect. A camera or smoke test of plumbing can reveal hidden issues.
If you spot a few, treat quickly. But stop storing damp rags, compost indoors, or over-watering plants near walls. Those habits feed the problem.
Expect control to take weeks, not days. Because of their lifecycle (egg-larva-pupa-adult) you’ll need monitoring, sanitation and follow-up treatments.
For phorid flies inside, you want a layered approach, identify and eliminate the breeding zone, fix moisture problems, monitor with traps, and use treatment responsibly. Then you’ll actually win.