Damp and moisture meters
The kitchen hood recirculates through a charcoal filter and there is no duct to outside. What moisture does that hood not remove from the room?
The hood does not remove moisture from the room. It recirculates air through a charcoal filter, and there is no duct to outside, so steam from cooking stays indoors. A charcoal filter is aimed at smells. It is not an outside discharge. The survey has recorded a recirculating hood and the absence of a duct. It has not measured humidity, and it has not tested the filter. The moisture produced at the hob is put back into the kitchen. Only a duct to the outside would take that vapour out of the dwelling.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
What is the fuller explanation?
Recirculating hoods draw grease and some odour through a filter and blow the same air back into the room. Water vapour passes that process. Without a duct through an outside wall or the roof, there is nowhere for the moisture to go except into the kitchen air, then onto cold surfaces if the room cannot cope. The survey saw the filter type and no duct. It did not weigh the moisture or run a performance test. The limit is the missing route outside.
If you want the moisture taken outside, that is a ducted hood or another outside extract, designed and fitted as new work. The survey has not specified that product. Tell the solicitor the kitchen hood recirculates and does not remove moisture from the room. A window or a separate fan, if there is one, is a different fitting and was not turned into a duct by this note. Do not describe the charcoal filter as if it dried the air.
What should you ask your surveyor?
- Does the hood recirculate through a charcoal filter?
- Is there no duct from this hood to the outside?
- Was moisture removal left unmeasured?
What are the typical next steps?
- Treat the hood as leaving cooking moisture in the room.
- Do not describe the charcoal filter as outside extract.
- If a duct is wanted, treat that as new work the survey has not designed.
Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.
Also asked about this
If the filter is new, does the hood then remove steam?
No. A new charcoal filter may help with smell. It does not create a duct. The hood still recirculates, so the moisture from cooking is not taken out of the room. The survey did not test the filter and did not measure humidity. Replacing the carbon leaves the same path: air back into the kitchen.
Does an open kitchen door into the hall count as the missing duct?
No. A door moves air between rooms. It is not a duct to outside, and it does not turn a recirculating hood into an extract. The moisture the hood fails to remove still starts in the kitchen and can spread through the house. The survey recorded no duct from the hood. An open door was not recorded as a substitute.