Extractor fan prob

Hi,
I live in a flat with an internal bathroom. It has an extractor fan that seems to be able to prevent the bathroom from steaming up very well, but somehow seems to suck in fumes from other bathrooms in the same block.
Looking from outside we seem to have an outlet on the outside wall (about 3m from the bathroom) on each floor but still we are getting smoke fumes from other flat's bathrooms.
We have an Xpelair extractor which has a flap behind the fan that only flaps 'outward' thus preventing air from coming in. We can only smell smoke coming in when the extractor is on - when it is off there is no problem. The extractor is sucking air out, but I assume not very efficiently.
My question is, is it the extractor that needs replacing or do I need to put some sort of backdraft "preventor" behind it? My innitial though is that the extractor needs replacing since the problem only occurs when the extractor is on so maybe it is just not powerful enough, and the exhaust from other fans in the block is coming back in through mine.
Any thoughts?! Any help appreciated.
-- Ant
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Anteateruk wrote:

3m is quite a way for a normal axial fan. A centrifugal model may be better.
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What do you mean by 'smoke fumes'? No bathroom should be emitting smoke! What actually comes back in?
If a fan is extracting, no matter how poorly, then it is very unusual for any air to be coming the opposite way through the duct. If the fan is pushing out, then air can not push back in.
The ducts should not be shared, unless there is a communal fan serving all ducts from all flats - which clearly does not apply to you.
You say that there is a vent from all flats, which indicates individual ducts. Now it is most unusual for someone else to be using their bathroom every time that you use yours and so push 'fumes' back into your property.
I would get your fan checked to make sure that the smell is not actually coming from the unit itself.
dg

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Thanks. I mean smoke as in cigarette smoke.. Sorry for being unclear! It doesn't happen everytime, but if we leave our fan on for a period of time then we nearly always end up with the smell of cigarette smoke in our bathroom. I agree that it sounds like the ducts are individual, but maybe the ducts I can see on the outside are from the boiler and not the bathroom - I was assuming that the bathroom and kitchen shared the same duct but this may not be the case.

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Anteateruk wrote:

horrible arrangement. You often come across them in hotels... I can see no possible solution other than increasing the power of your fan to keep the neighbour's fumes out.

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Cigarette smoke would have to be in a very large concentration to get in through the duct from outside, plus I can't see how it could get in as to be detectable if the fan is extracting out.
Is there any other way the smoke could be getting pulled into the room by the fan - i.e. through any gaps in walls , behind units etc? If the fan is extracting it is pulling air into the room, and this air could be containing the smoke.
Some of our high-rise flats had problems with cooking odours getting in through open joints and cracks between wall and floor concrete panels. These were hidden behind timber panels and cupboard units and were hard to trace. We initially thought it was due to close proximity of vents and open windows, but this was not the case.
If you are in a flat then any ingress of smell is potentially serious as the flats should be compartmentised in case of fire in an adjacent flat. If smoke is getting in then so could smoke and flames from a fire.
You should have a service agreement with a management agency for repairs to the structure, and I would contact them without delay to investigate.
dg

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dg wrote:

Same conclusion as me, DG, and your advice is better.
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"Anteateruk" wrote | Thanks. I mean smoke as in cigarette smoke.. Sorry for being unclear! | It doesn't happen everytime, but if we leave our fan on for a period | of time then we nearly always end up with the smell of cigarette | smoke in our bathroom.
The air that the fan extracts from the bathroom has to be replaced from somewhere. Possibly it is being replaced, not by air from your own hall, but by air being sucked from an adjacent flat. I'd have a look at the boxing-in of pipes esp the soil stack and underneath the bath panel.
Owain
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Thanks to everyone for their help. The problem is with the air being sucked in from another flat - the cistern is kind of built into the wall, taking the cover off of this there is a strong smell of smoky air. I can't see where all of the pipes go but I assume that the sewage pipe at least must join up to other sewage pipes in the block and there is probably not a complete seal between each flat. Would my management company being legally abliged to do something about this or is this normal?
Thanks again to everyone who replied.
--
Ant



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--
Chris Green ( snipped-for-privacy@x-1.net)

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Chris Green wrote | Owain wrote: | > The air that the fan extracts from the bathroom has to be replaced | > from somewhere. Possibly it is being replaced, not by air from your | > own hall, but by air being sucked from an adjacent flat. I'd have a | > look at the boxing-in of pipes esp the soil stack and underneath the | > bath panel. | Exactly what I've just said (differently)! :-)
A combination of great minds and off-line newsreaders.
Owain
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Hello Anteateruk

Sure the fumes aren't coming through the floor or ceiling, and by activating the fan you're sucking them through?
Could try with the door open and see if that fixes it - otherwise you're sucking the air out of a room; it's either going to come in from *somewhere* or your bathroom will implode.
--
Simon Avery, Dartmoor, UK
uk.d-i-y FAQ: http://www.diyfaq.org.uk /
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Anteateruk wrote:

Well, if it is, the chances are that you have a path to the other rooms via some unseen pipe run or somesuch. The fan must be sxtractingf, so where is the air getting IN to the bathroom?
You are supposed to have e.g. a hole in the door, or a gap underneath, to let air in from the rest of your property. If it ain't there, the air will come from wherever it can. Possibly over a ceiling void, through holes punched in walls and floors for pipes etc etc.
A few weeks ago, there ws this terrible smell in a room with and extractor...traced it to a giant puppy turd miles away up the hall. Yup. Thats how far the air had moved towards te extractor..
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There is a gap underneath the door and slight gap all the way around (big enough to see light through) - maybe a vent in the door would be a good idea?

Really? Lol!
-- Ant
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out of your bathroom, air is being sucked in somewhere else in your flat and it's the sucked in air that carries the smells. So no amount of messing about with the extractor is going to fix the problem.
--
Chris Green ( snipped-for-privacy@x-1.net)

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