Hi,
For some reason, it seems that every time we turn on the air conditioning, our house becomes infested with flies. I guess it's possible that these flies are coming in when we open the door, but is it possible it's coming through the vents?
Thanks.

Let me ask you a couple of questions. First, is your A/C a central unit and if it is... is it refrigerated air or an evaporative system? Have you noticed more flies in one room or another or do they seem to just appear? Are they regular "house flies" or are they unusual in size or color?

It might help to know what part of the world you live in. I suppose you probably already checked your filter(s).

a/c is a central unit. I think it's refrigerated air. The flies just seem to appear, but usually on the main floor. However, they seem to fly around mostly in the parts of the house that's really sunny. As far as I can tell, they are regular house flies. We change the filter regularly. It doesn't seem to make a difference.

We live in silver spring, md.

Thanks for you help.

Your problem with the flies is a tough one to solve. In the pest control business, one of the primary philosophies is "S.O.S." (seek out source). I would guess that when the A/C is on it probably creates a small increase in the air pressure inside your home that would normally cause air to flow out, when a door or window is opened. Although the flow is probably negligible, there may be a similar condition that is providing an in-flow of air from the outside when the system is on. Have you checked your attic? Do you keep anything around the outside walls of your home that could be providing a breeding area for the pests?

I wish I could help you more.

We haven't checked the attic, but we never open the attic door. We'll check outside the house for breeding areas.

Thanks so much for trying.

Do you ac system have fresh air intake

How can I tell if my ac system has fresh air intake?

How I can tell if my ac system has fresh air intake?

Check the Control Panel again, Can you spot Fresh Air Intake, switch their?

1. Main Ac Switch. (Electrical Switch which control the fan motor & compressor.)
2. Thermostat Switch. (Electrical Switch which control the Temp of the room)
3. Air Swing Switch. (Electrical Switch control flow of the out put air of the ac)
4. Exhaust Switch/Knob (Mech Switch/Knob which open/closes a small window)
5. Fresh Air Intake Switch/Knob (Mech Switch/Knob which open/closes a small window)

how can i tell if my ac system has fresh air intake?you ac : do you have fan inside the closet/attic ?the look for a duct(non exhaust) that lead to the outside... or a package unit( both indoor/outdoor fan/coil packed together),it have a hood that facing down with 1/4in screen holes... the fly usually don't come through the ac , unless you have an dead animal or garbage near by

Something may be in your air vents ask your orkin man about it or something!

We had this problem a few years ago. It turned out that the flies were nesting in the AC ducts and hatching every spring, (possibly when the air first went on) We had the problem 3 years running. Eventually we realised they were coming from the ducts. Had them cleaned and as I recall treated with a fly spray and we finally rid ourselves of the pests

WE had this problem a few years ago - 3 years in a row.
Finally discovered flies were nesting in the AC ducts. Hatching presumably about the time the AC came on in spring.
Clean the ducts and see if you can get bug spray in the vents.

WE had this problem a few years ago - 3 years in a row.
Finally discovered flies were nesting in the AC ducts. Hatching presumably about the time the AC came on in spring.
Clean the ducts and see if you can get bug spray in the vents.

Frand, they probably no longer have the problem. The date of a post is in the upper left corner. Please take note of them in future. Otherwise this is a very good answer.

However, just to keep newer questions at the top of the page, I am closing this thread.