We moved some time ago and in the new washroom there is a lot of dust on the surfaces (I clean it nearly every day but next day there is a new layer). Only source I could imagine is the ventilation system. My guess is there is a missing part like a fabric layer or something on top of the shown part on the picture.

Is this assumption right and how could I add it?

mentioned part

Addition: On one outer side of the washroom is a fireplace. Once we start the ventilation (button for it like for light) when the fireplace is burning, the smoke comes into the washroom.

  • 1
    This is supposed to be an exhaust fan. When the fan is on, which way is the air flowing? – JACK Jan 28 '20 at 13:01
  • The air goes from the room into the "wall" – Allerleirauh Jan 28 '20 at 14:20
  • I think you answered your question with the fireplace. – JACK Jan 28 '20 at 14:55
  • That much smoke in your home is not healthy at all. Even "clean" wood smoke is highly carcinogenic. You need to address this issue or discontinue use of the fireplace. – isherwood Jan 28 '20 at 16:03
  • Bath and bedrooms are normally the dustiest rooms in a home because of tiny bits of fiber that breakoff of towels and blankets and are dispersed into the air by use of the fabrics. – blacksmith37 Jan 28 '20 at 17:03

Your exhaust fan is bringing smoke/soot into your bathroom. Your fan is operating correctly and no screen or filter on it will solve your problem. Make sure the flue for your fireplace is completely open. You might want to keep your bathroom door closed when the fireplace is in use, or at least don't use the fan.

  • So we do. Door (opposite wall than fireplace) is closed and fan is not used since this one experience. The chimney is opened complete every time the fireplace is in use. But anyway the dust is in the bathroom. May a little frame with fabric filter in front of the fan is missing? – Allerleirauh Jan 28 '20 at 15:46
  • Even one problem is solved. We had a professional chimney cleaner to have a look on it, and he around an half an hour make ash raining into the fireplace. The chimney seems been cleaned the first time ever, no law covers this issue here. Now there is no smell of fire in any of the rooms, equal which flaps are open or closed. – Allerleirauh Dec 11 '20 at 13:38

A screen or a filter won't fix this problem.

Air should not be coming in through that vent. Something in your house is causing negative air pressure, and it's pulling in air through that vent. The outside of that vent should have a flap that is normally closed, and when the fan is on the air pressure opens it. If that flap is missing or not working, then you need to get that fixed.

If it gets worse when there is a fire in the fireplace, you have a potentially dangerous situation. Combustion byproducts are a serious hazard.

  • Could you imagine someone had the "brilliant" idea to place this flap inside the chimney? – Allerleirauh Jan 28 '20 at 17:38
  • Are you talking about the damper? Yes, there should be one of those in the chimney, too. But I'm talking about the bathroom exhaust fan. You keep asking about a filter. We are telling you that something else is wrong, and a filter is not the correct answer. You have a negative air pressure problem, and your exhaust fan is missing it's damper. – longneck Jan 28 '20 at 20:27

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