Smoke Odour Removal Methods — What IICRC S700 Certified Contractors Use

Smoke particles produced by a house fire range from 0.4 to 0.7 microns in diameter — small enough to penetrate porous building materials including plasterboard, timber framing, insulation batts, and ceiling cavities. Unlike surface soot, which can be wiped away, smoke compounds absorb into the molecular structure of these materials and off-gas odour long after visible residue is cleaned.

A further complication is the HVAC system. Smoke drawn into return air ducts during a fire is distributed throughout the building, depositing residue in ductwork, on coils, and in every room served by the system. This is why properties can have strong smoke odour in rooms remote from the fire origin.

The type of material burned also affects the odour compounds produced:

• Protein fires (cooking fires, animal matter) — produce a near-invisible but highly penetrating residue with strong, acrid odour
• Synthetic fires (plastics, rubber, foam furniture) — produce heavy, oily soot with pungent petrochemical odour
• Paper and wood fires — produce dry, powdery residue with a more familiar smoke odour that is easier to treat

Each fire type requires a different deodorisation approach. IICRC S700:2025-certified contractors are trained to identify the fire type and select appropriate methods for the specific odour compounds present.

IICRC S700:2025 certified contractors use a combination of deodorisation methods depending on the materials affected, the severity of odour penetration, and whether the property is occupied during treatment.

Thermal Fogging

A petroleum-based or water-based deodorising solvent is heated through a fogging machine to create very fine particles — typically 0.5–5 microns — that suspend in air and penetrate the same porous surfaces that absorbed smoke. The fog follows the exact pathways the smoke took, reaching inside wall cavities, ceiling spaces, and the grain of timber. Thermal fogging is most effective for structural deodorisation where soot has penetrated framing and cavities. The property must be unoccupied during treatment and ventilated thoroughly before re-entry.

Ozone Treatment

Ozone generators produce O₃ molecules that react with and oxidise smoke compounds at a molecular level, breaking the odour-causing chemical bonds. Ozone is highly effective for absorbed smoke odour in soft furnishings, carpet, drapes, and timber surfaces. Treatment requires an unoccupied property — ozone at treatment concentrations is harmful to people, pets, and plants. A typical treatment runs 4–24 hours followed by a ventilation period before re-occupancy. Ozone is not suitable for properties with rubber seals or certain sensitive materials.

Hydroxyl Generators

Hydroxyl generators produce OH radicals using UV light and water vapour, which break down odour molecules continuously over time. Unlike ozone, hydroxyl treatment is safe for occupied spaces — people, pets, and sensitive materials can remain on-site during treatment. Hydroxyl generators work more slowly than ozone (treatments typically run 3–7 days continuously) but can be used in situations where ozone treatment is not safe. They are particularly useful for ongoing odour control during the restoration phase.

HEPA Air Scrubbing

HEPA air scrubbers filter airborne particles — including smoke soot at sub-micron levels — from the air within a confined space. Air scrubbers address airborne contamination but do not treat odour compounds absorbed into structural materials. They are used in combination with fogging or ozone treatment to reduce airborne particle load and improve air quality during and after deodorisation. HEPA filtration is also used during the demolition and cleaning phases to prevent re-contamination.

ANSI/IICRC S700:2025 is the professional standard for fire and smoke damage restoration in Australia. Certified contractors follow a structured deodorisation protocol that ensures complete treatment and produces the documentation your insurer requires to close the claim.

• Why certification matters — an IICRC S700:2025-certified contractor is trained to identify all affected materials, select appropriate deodorisation methods for each surface type, and treat the full extent of smoke migration — not just the burned room
• Insurance documentation — a certified job produces a written scope of works, treatment records, and a completion report confirming deodorisation to standard; this documentation is required for insurance sign-off
• Post-treatment clearance — clearance testing confirms odour levels have been reduced to acceptable levels before the claim is closed
• HVAC decontamination — IICRC S700:2025 includes HVAC system assessment and decontamination as a required component where the system was operating during or after the fire

For the full ANSI/IICRC S700:2025 standard, visit iicrc.org.

HVAC systems are a primary vector for smoke cross-contamination. When a fire occurs in a property with a ducted system operating, smoke is drawn into return air grilles and circulated throughout every room served by the system — depositing soot on coils, inside ductwork, and on supply diffusers throughout the property.

Even when the system was not operating during the fire, smoke can enter ductwork through supply and return grilles by diffusion, especially in a smoke-filled environment over hours.

HVAC decontamination after a fire involves:

• Duct cleaning and fogging — physical cleaning of accessible ductwork followed by thermal fogging through the duct system to deodorise internal surfaces
• Coil and air handler cleaning — evaporator and condenser coils are cleaned and treated to remove smoke residue that would otherwise re-contaminate the air on every heating and cooling cycle
• Filter replacement — all filters are replaced; existing filters that captured smoke particles must be discarded, not cleaned
• Post-treatment air quality testing — air quality is tested after HVAC decontamination to confirm particulate and VOC levels are within acceptable ranges before the system is returned to service

Failing to decontaminate the HVAC system is one of the most common reasons smoke odour returns after restoration work is completed. Each time the system operates, residual smoke compounds in the ductwork are recirculated into the living space.