Smells that are not yours almost always travel through the shared ventilation shaft. Treatment removes what has already soaked into your home, but the cross-flow itself has to be dealt with another way.
In a block of flats the kitchen and the bathroom share a ventilation shaft. Each flat connects to it with its own duct, and in a properly working system air from all the flats travels in one direction — up and out through the roof.
The problem starts when the flow reverses somewhere in the shaft. Air from one flat then does not leave the building but flows into the grille of the flat next door or above. Everything in that air comes with it: the smell of fried food, cigarette smoke, damp from a bathroom, cleaning products.
That explains why the smell often arrives in waves — in the evenings, at particular hours or at a specific time. You are noticing the moments when a neighbour is cooking, smoking or using water, not a constant background smell.
One thing is important to understand: air always moves from higher pressure to lower pressure. If your flat has sealed windows and the extractor hood is running, your flat becomes that lower-pressure place, and air is drawn into it from everywhere — from the shaft, from gaps, from the stairwell. So a lack of fresh air inlet is often not a separate problem but exactly what lets a neighbour's smell in.
Very often people describe the same thing: everything was fine for years, and then it suddenly started. The reason is usually mechanical.
The commonest of them — somebody in the building has fitted a powerful extractor hood and connected it directly into the shared duct. A hood like that pushes far more air into the shaft than it can carry away. The resulting overpressure looks for another way out, and it finds one through the grilles of the neighbouring flats. As a result, the ventilation in your kitchen starts working in reverse.
Other typical reasons:
A simple self-test: hold a thin sheet of paper against the ventilation grille in the kitchen and in the bathroom while a window is slightly open. If the sheet stays against the grille, the duct is drawing. If it falls away or moves off, the draught is weak or reversed. More on this on the Ventilation in a flat page.
It is important to separate two things here, because you can only solve part of them inside your own flat.
| Issue | Where it is dealt with | What it achieves |
|---|---|---|
| Gaps around pipes and the riser | In your flat | Stops direct cross-flow through the structure |
| Socket and switch boxes in a shared wall | In your flat | Closes a route that is often overlooked |
| Your own ventilation grille is dirty | In your flat | Improves extraction from the room itself |
| Non-return valve on the grille | In your flat | Reduces backflow but weakens ventilation |
| Silted-up shared riser | Property manager | Restores draught for the whole riser line |
| Hood connected into the shared duct | Property manager | Removes the cause of the overpressure |
| Damaged shaft cowl on the roof | Property manager | Restores the air outlet |
While the building issue is being sorted out, simple everyday measures help too:
None of these deals with the cause, but they noticeably reduce how much foreign air enters the flat over a day.
Ozone treatment removes the smell that has already soaked into your flat, but it does not stop the cross-flow. If a neighbour's air keeps coming in through the grille, the smell will return in time.
And now the honest part about our work. Ozone treatment removes the smell that has already soaked into your flat — into textiles, soft furniture, curtains, clothes in the wardrobe, finishes. After treatment the flat is clean. But ozone treatment does not stop the cross-flow: if a neighbour's air keeps coming in through the grille, the smell will come back after a while. How quickly depends on how intensive the flow is.
So we say this up front rather than selling repeat treatments. Ozone treatment makes sense here in two cases: when the cross-flow has already been dealt with and the remaining smell has to go, or when you need a clean flat for a specific moment — letting it, selling it, moving into a new place.
A third option is real too: you know the building issue will drag on for months and you simply want the accumulated smell out of the flat in the meantime. That is your decision, and we will do it as long as you understand what you are buying.
If the neighbour's smell is tobacco smoke or damp and mould, Musty mould smell will also be useful, along with the other sections on the Odour removal page. For more on the method itself, read Ozone treatment and Air disinfection.
We check where the smell is stronger — at the grille or at gaps in the structure.
We assess whether your duct is drawing or working in reverse.
We point out the places where air crosses through the structure and what can be sealed.
We treat the room, the textiles and the soft furniture that have taken up the smell.
We air the premises and tell you what has to be dealt with at building level.
Ozone treatment €1.20/m², minimum €60. If surface treatment is also needed, we set the price after an inspection.
No. It removes the smell that has already soaked into your flat, and after treatment the place is clean. But if air from the neighbour's flat keeps coming in through the ventilation, the smell will gradually return. We say that up front.
It often helps and costs little. The essential condition: if it is the only duct in the room, the ventilation becomes weaker, so a fresh air inlet has to be provided, for example a window trickle vent or a wall valve.
The ventilation riser is common property, so the matter is dealt with by the property manager — with a written request for the draught to be checked. If several flats on the same riser sign the request, it is usually handled faster.
Describe the situation — we will tell you whether treatment is needed at all, and which one.
Fill in the form — we will call you on the number you provide, ask a few clarifying questions and propose a solution.
Thank you! We will contact you on the phone number you provided shortly.
