Toilet extractor fan solution after extension - carbon filter?

[velodocuk]

We've extended onto a wall that contained the outlet for an internal toilet extractor fan. So temporarily, this fan ducts into a cavity.

The original plan was to re-route the ducting to the other side of the house. But this seems tricker than expected - we'd have to destroy a lot of ceilings, fix a long run of ducting just to get to the nearest outside wall. Even then - that wall contains the outlet for the CH condensor boiler so it may not be a good idea to come out too near that.

We've had the suggestion that ducting into a cavity from a toilet only room (not a bathroom or shower with moist air) can be acceptable if you use a fan with a carbon filter for odour control.

But I can't seem to find any such fans - does anyone know if they exist?

Thanks Paul

[Owain]

No. The purpose of the extractor fan is to extract the air to the outside, not pump it into the wall cavity and hope it makes its way outside somehow.

When you flush the toilet, aerosolised fecal matter laden with bacteria is sprayed into the air. It is this which you need to extract to the outside, rather than 'odour' per se. Using a carbon filter for odour control is only of relevance if you are using a recirculating fan; using one would be an admission that your fan is not extracting from the room space.

If you can't take the long way across the extension can you go up through the roof? Or even down and under the floor? Oblong ducting will run parallel to joists quite easily.

Owain

[Pete C]

Didn't your mum teach you to shut the toilet lid before flushing? :)))

cheers, Pete.

[Owain]

The aerosolised fmlwb then hangs around in the toilet bowl waiting for the next user to lift the lid.

Owain

[<me9]

If you lower the lid the aerosol leaves the pan at higher velocity through the gap, and travels further. Unless it is a hermetic seal (which it never is) it is better to leave the lid up.