I recently had a fruit fly infestation and found that they were nesting in the tracks of the sliding door. I have since removed the nest and have had all my windows cleaned. I never see any flies anymore that is until I cook. I have all my drains closed all the time even the shower drain so they can't be nesting there. I usually cook about once a week and I roast broccoli which stinks up the whole house. Usually 5 or so come out when I cook. Could they be coming from outside? I had the pesticide company come out twice and they said my place was so clean and I was doing all the right things, they don't know where they could be coming from. I have a Katchy machine so that usually catches them after a few days. But not being able to eat every time I cook is frustrating. I can't imagine where they are coming from.