Removing damp smell

What this smell means

That characteristic musty smell is not “the smell of air” and it is not the smell of dust. It is produced by volatile compounds released by growing mould and bacteria — a kind of metabolic by-product. Mould breaks down the organic material it feeds on: paper in wallpaper, adhesive, timber, dust, additives in plaster. That process puts compounds into the air which the human nose detects at very low concentrations.

There is one practical conclusion, and it matters: the smell is a sign of a process, not a separate problem. If a room has this smell, biological growth is happening right now somewhere in the room or in the structure. Ozone treatment removes the smell but does not stop the growth, because it does not remove the moisture the growth lives on.

If you can smell it but cannot see it

A second conclusion: if you can smell it but cannot see any mould, that usually does not mean there is none. It means it is somewhere you cannot see — behind the finish, under the covering or inside the structure.

A damp smell is a symptom. Treat the symptom and the cause stays and comes back.

Where to look for the source

The smell spreads through the whole flat, so the room where you notice it most is not necessarily the room with the problem. Look for places that have both moisture and still air.

• under the floor covering, especially if there was ever flooding or a leak;
• behind fitted wardrobes against an external wall — the surface there is colder and the air does not move;
• in ventilation ducts, where a layer of damp dust has built up;
• under the sink, behind the bath, behind the toilet and behind the fridge;
• in the basement or the attic, from where the smell travels through the stairwell and the shaft;
• in soft furniture and mattresses that have stood for a long time in a damp room.

The type of building makes a lot of difference.

A concrete example: a 54 m² two-room flat in Purvciems, a smell in the bedroom, no visible mould. Behind a fitted wardrobe against the external wall the moisture reading is elevated, and when the wardrobe's back panel is removed there is a dark patch on the wall about 0.5 m² in size. The wardrobe stood tight against the wall, the air behind it did not move, and in winter the surface there was a couple of degrees colder than the rest of the room. This is one of the commonest configurations of all.

A useful technique: coming home after a longer absence, the smell is far more obvious. The nose gets used to a constant background within a few days, so in your own flat you do not register it. If you can, ask someone who has not been to your place to judge it.

Why the smell changes with the seasons

In the Latvian climate a damp smell is almost never even across the year, and it is precisely those changes that help identify the cause.

Summer has its own specifics with basements. When warm, humid outdoor air flows into a cool basement, the moisture condenses on the cold walls — so airing a basement on a hot day makes the situation worse, not better. It makes sense to air a basement in cool, dry weather, usually at night or early in the morning.

What to check yourself

Part of the answer can be obtained without any specialist, and that changes what is worth ordering at all.

• Buy a cheap humidity meter and leave it in the problem room for a week. Consistently above 65% means the cause is in the air exchange or in the structure.
• Pull furniture at least 5–10 cm away from external walls and check the wall behind it, including the wardrobe's back panel from the inside.
• Lift a corner of the floor covering where there was once flooding — the subfloor underneath tells you more than the surface does.
• Check the ventilation draught with a sheet of paper held at the grille while a window is slightly open.
• Check whether condensation forms regularly on window glass and in external wall corners in winter.
• Ask someone who has not been to your place to assess the smell — you no longer perceive it objectively yourself.

If the moisture is only in the air but the structure is dry, the answer is often a change of ventilation routine and a dehumidifier rather than treatment. If the structure itself is damp, you first have to find where the water is coming from.

How we remove it

With a damp smell, ozone treatment is the last step, not the first. If we do it first, the smell disappears for a couple of weeks and then comes back — that is simply a waste of money and time.

There are also cases where we advise you not to order treatment. If the readings show that the structure is wet and the cause has not been dealt with — a roof leak, damaged waterproofing, a burst pipe in a wall — that has to be sorted out first. Treatment before then is an expense with no result, and we say so at the outset, not after the job.

If we find mould during the inspection, the scope changes: it is no longer odour removal but mould treatment with removal of the affected material. More on this on the Mould removal and Musty mould smell pages.

Prices

Inspection with moisture readings from €40. Ozone treatment €1.20/m², minimum €60. If we find mould, treatment starts from €1.50/m² — more detail on the Mould removal page.