This is my first time living in an apartment in the summer. I'm living in New York City. Every day, we spot a new fly, and we kill it.

I can't detect how flies are entering my apartment! My husband and I have watched each other opening and closing our main door when we leave and return home — we see no flies. Is it possible that flies are flying through the exhaust duct in our balcony, and entering through the kitchen fan? Can we rule out the possibility or not? See below — our Sakura R-727II doesn't have any filters.

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The duct from your kitchen exhaust fan (and from bathroom exhaust fans) extend to the exterior of the building.

Those ducts have what is called a “backdraft damper”. The damper is weighted in such a manner that it closes when exhaust air is NOT being exhausted to the exterior.

That is to say that if the duct goes through a wall, then the backdraft damper is a flap and if it goes through the roof, then opposing dampers close within the duct.

These dampers are usually installed at the end of the duct run rather than at the beginning, because it keeps bugs from making nests in the ducts and it’s easier to fix outside rather than inside.

I suspect 1) you’ll need to find and fix these dampers , or 2) install a new screen in the existing exhaust fan unit.

I suspect you have an exhaust fan screen and have not found it yet…or a previous tenant took the screen and tossed it because it was too difficult to clean. Either way I’d find the exhaust fan manual (or look it up on the internet with the make and model) and order a new screen.

  • All of this is absolutely true, but buildings are porous. There are many ways flies can get in and out. Do what's recommended above, but don't be surprised if this isn't the end of it. Jul 20 at 14:01

There should be a screen on the vent at the exit, similar to a window screen.

If there's no screen there, adding a filter to the fan unit might be easier. A search for "Sakura R727 filter" found some options, but I haven't deeply investigated them.

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