Bad smells at home: causes and how to fix them

Does your home smell unpleasant even though you clean regularly? Start by finding out where the smell comes from. A musty smell may be caused by damp or mould in the building, but it can also come from drains, poor ventilation, old building materials, smoke or pets. The right solution depends on the cause: a dehumidifier helps with excess humidity, while an air purifier can reduce certain airborne pollutants. Neither replaces dealing with the source of the smell.

Common causes of unpleasant smells at home

The type of smell and where you notice it may offer clues, but smell alone rarely identifies the cause. Common sources include:

• Damp in a crawl space or basement: Ground moisture, water ingress and humid outdoor air can contribute to musty smells. Read more about damp in crawl spaces.
• Moisture damage and microbial growth: Mould and other microorganisms can grow in damp parts of a building, including behind finishes or in the loft.
• Drains: Dried-out water traps, deposits or faults in the drainage system can cause sewage smells in kitchens and bathrooms.
• Inadequate ventilation: Cooking smells, moisture and other pollutants can linger when the ventilation does not work properly.
• Smoke, pets and textiles: Odour-causing substances can become trapped in carpets, furniture, curtains and other materials.
• Paint and building materials: Some materials and products release substances with a chemical or stale smell, particularly during renovation.

What do mould and moisture damage smell like?

A damp building structure may smell earthy, stale or musty. Sometimes the smell is most noticeable when you open a crawl-space hatch, go down to the basement or return home after the house has been closed up. Smells can also enter the living areas through gaps and leaks.

However, a musty smell is not proof of mould, and moisture damage does not always produce an odour. If you notice visible staining, damp materials or suspected growth, the structure needs investigating. You can also read our guide to mould in crawl spaces.

In some older houses, timber previously treated with chlorophenol-based wood preservatives can give rise to chloroanisoles. These can produce a mould-like smell without necessarily indicating active mould growth. If you suspect this, a building surveyor may need to investigate the materials and the source of the smell.

See also research on chloroanisoles and mould-like odours.

How to find the source of the smell

1. Locate the smell. Is it strongest in the bathroom, near the floor, in the basement or by the loft hatch? Note whether it changes after rain, showering or when the ventilation is running.
2. Rule out simple causes. Check water traps, floor drains, rubbish, textiles and visible dirt. Make sure ventilation outlets and filters are maintained according to the instructions.
3. Look for signs of damp. Check for condensation, staining, damp materials and leaks. It is useful to monitor temperature and relative humidity over time, but a single reading cannot prove or rule out damage.
4. Get help if the cause is unclear. Persistent smells from foundations, walls or roofs may require a building survey or moisture assessment by a specialist.

The Swedish Public Health Agency explains why both odours and suspected moisture damage may warrant further investigation.

How do you get rid of unpleasant smells at home?

Always start with the cause. Air fresheners and other products that mask smells will not fix hidden moisture damage or a drainage problem.

If the smell is caused by damp

Repair leaks and deal with ground moisture, drainage issues or other sources of damp first. If the area still has excessively high humidity for extended periods, a desiccant dehumidifier can help keep moisture under control, for example in a crawl space or cool basement. It cannot, however, remove existing mould or odours already embedded in damaged materials.

If the ventilation is not working properly

Check that the ventilation system is working and maintained as intended. Insufficient air exchange can leave smells and moisture trapped indoors. In some houses, a mechanical ventilation unit with heat recovery may form part of a long-term ventilation solution, but the need must be assessed in light of the building's construction and existing system. Incorrect changes to airflow can cause new problems.

If you want to reduce particles and certain odours

An air purifier with a particle filter can reduce airborne dust, pollen and smoke particles, for example. Filters specifically designed for gases and odorous compounds, such as activated carbon filters, may also reduce some of these substances. Effectiveness depends on the substance, filter and airflow. An air purifier cannot guarantee the removal of every smell or replace remediation and ventilation.

If the smell comes from drains or materials

Clean or repair the actual source. A faulty water trap or leaking drainpipe needs fixing. Smoke or pet odours may require thorough cleaning or replacement of affected materials. Odours from older building components may need investigating before you choose a remedy.

When should you call a professional?

Get help if the smell is strong or keeps returning, if you suspect moisture or mould damage, or if you cannot find the source. If you suspect a gas leak, smoke or a burning smell, treat it as an immediate safety concern and contact the appropriate emergency service rather than trying to cover up the odour.

If you have investigated the problem and need help choosing a dehumidifier or air purifier, we can show you which of our products may be suitable. Find the cause first, then choose the right solution.