Decomposition produces gases and organic compounds during the natural breakdown process. These can create an extremely strong and persistent odour inside a house, flat or other enclosed property.

There is no single fixed period for how long decomposition smell lasts. If biological fluids or odour-producing contamination have entered absorbent materials, the smell may remain for weeks or even months until the affected materials and underlying surfaces are properly treated.

What affects how long decomposition smell lasts?

The following factors can influence the strength and persistence of the odour.

Why can decomposition odour remain after the deceased has been removed?

Removing the deceased does not necessarily remove the source of the odour from the property. Biological fluids and decomposition compounds may have entered materials in and around the affected area.

These can include:

• carpets and underlay
• mattresses and upholstered furniture
• wooden flooring and subfloor materials
• laminate flooring and joints
• skirting boards
• plasterboard and wall cavities
• insulation and other porous building materials

Odour can continue to be released from these materials even when visible contamination has been wiped away. This is why surface cleaning alone may be insufficient.

Will opening windows remove decomposition smell?

Ventilation can make the odour less noticeable temporarily by allowing gases to escape and fresh air to enter. However, opening windows does not remove contamination from flooring, furniture or structural materials.

If the smell returns after the property has been ventilated, this can indicate that an odour source remains inside the affected area.

Why ordinary cleaning products may not work

Domestic disinfectants, bleach, scented sprays and carpet cleaners are not designed to identify or remove contamination hidden underneath flooring or inside porous materials.

Attempting to mask the smell can also make it harder to establish where the odour is strongest. Where bodily fluids or decomposition contamination are present, unnecessary contact with affected materials should be avoided.

How specialist cleaning removes decomposition odour

Effective odour treatment begins by identifying and dealing with the original source. Depending on the condition of the property, professional work may include:

• assessing the full extent of the affected area
• removing contaminated furniture and soft materials where necessary
• lifting affected carpet and underlay
• inspecting and treating flooring or subfloor surfaces
• cleaning and disinfecting affected hard surfaces
• using professional air filtration or odour-control equipment where appropriate
• handling and disposing of contaminated waste safely

Odour-control equipment should not be treated as a substitute for removing the contamination source. If affected materials remain untreated, the smell may return.

When should professional help be considered?

Professional advice should be considered when:

• there is visible biological contamination
• a person remained undiscovered for a period of time
• the odour remains after ventilation
• carpets, mattresses or upholstered furniture were affected
• fluids may have reached flooring or structural materials
• the affected area cannot be safely cleaned using normal household methods

Not every death inside a property requires specialist cleaning. Where there is no biological contamination, ordinary cleaning may be sufficient. The condition of the individual property should determine what work is required.

Where the death was not discovered immediately, read TrustedCare’s guide to unattended-death cleaning.

Can decomposition smell return after cleaning?

Yes. Odour may return if contaminated material remains underneath flooring, inside furniture or within another concealed area. Temperature changes can also make residual odours more noticeable.

A smell that repeatedly returns should be investigated rather than repeatedly covered with fragrances or air fresheners.

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