Soot and ash after a wildfire: how to clean a home or office without making the contamination worse

The fires that hit the Fontainebleau forest from 12 July 2026 — more than 2,000 hectares across Seine-et-Marne and Essonne — followed by those in the Var and several other départements, produced a consequence that is consistently underestimated: soot, ash and dust falling well beyond the perimeter of the flames. Thousands of homes and commercial premises that were never threatened by fire now have a grey film on window ledges, terraces, desks and floors.

This is very different from conventional post-disaster restoration. There are no burnt materials, no weakened structure, no drying to organise. There is a deposit of fine particles, often invisible on dark surfaces, and a precise health protocol published by the regional health agencies. That protocol runs counter to almost every ordinary cleaning reflex. This article sets it out, then extends it to a case nobody covers: offices, shops and commercial buildings, where mechanical ventilation turns a local problem into building-wide contamination.

What the health authorities actually say

The guidance published by the French regional health agencies during the 2026 fires is remarkably consistent from one region to another. It splits into two phases: during the smoke episode, and afterwards, particularly in areas that were evacuated. Here is what it contains, without interpretation.

During the smoke episode

The guidance is defensive: limit trips outside and time spent outdoors, postpone intense physical activity, keep doors and windows closed and only air when conditions allow, cover air vents with damp cloths, shut down mechanical ventilation during smoke episodes, avoid anything that degrades indoor air quality (incense, candles), and keep an eye on at-risk individuals. Direct exposure to smoke warrants an FFP2 or FFP3 filtering mask. A simple unpleasant smell or upper-airway irritation does not warrant calling your GP or the emergency number.

Protective equipment first

Cleaning does not start with a product, it starts with protection. Three rules:

• Gloves for all cleaning and restoration work, to avoid any direct skin contact with soot, ash and dust.
• An FFP2 mask, recommended for at-risk individuals and pregnant women, and required wherever residual smoke remains.
• Children under 6 kept away until the premises have been cleaned. Older children should spend limited time on site and be offered a correctly sized FFP2 mask.

The right cleaning reflexes

This is where the official protocol surprises most people:

• Air every room thoroughly first — but only once the smoke has cleared.
• No vacuum, no blower, no pressure washer, no dry sweeping, indoors or outdoors (terrace, garden furniture). These practices put dust, ash and soot particles back into suspension.
• Clean with water only: a damp mop for floors, damp wipes for objects and furniture.
• Wash hands with soap and water after removing gloves and after any outdoor activity. Cleaning clothes are removed and washed separately, and textiles (curtains, rugs, clothing) are never shaken indoors.

Garden, water and pets

Where soot or ash is present outdoors: do not eat garden produce covered in deposits, wash fruit and vegetables with water before eating and peel root vegetables and tubers, and as a precaution do not eat eggs from private henhouses. After a prolonged absence, run indoor taps for two minutes before drinking the water — that water can be reused for household cleaning. For pets: clean bowls, wipe paws after each outing, and stop them licking ash deposits. Children's toys are cleaned before reuse.

The 5 actions that make contamination worse

In the field, the same mistakes are what turn a half-day clean into a multi-day job. None of them is intuitive to avoid.

1. Vacuuming first

The reflex action, and the worst one. It redistributes the finest particles — those that penetrate deepest into the respiratory tract — throughout the room, including rooms already cleaned. If you take away one thing from this article, take this.

2. Bringing out the pressure washer for the terrace

High pressure aerosolises the deposit and drives it towards façades, windows and air inlets. It also forces greasy soot into porous surfaces — reconstituted stone, exposed aggregate concrete, timber — where it becomes considerably harder to extract. On a terrace, rinse at low pressure, with water, draining towards a low point.

3. Wiping dry, with a cloth or dry microfibre

A dry cloth does not capture soot: it spreads it and lifts it as microparticles. On light-coloured surfaces it also leaves grey streaks that are very hard to recover. Microfibre remains an excellent tool — but damp, folded into quarters, and turned to a fresh face on every pass.

4. Going straight in with a scented product

A scented cleaner or air freshener does not remove burnt odour: it masks it for a few hours, then combines with it. Aerosol products further degrade indoor air that is already loaded. The correct sequence is mechanical removal of the deposit with water, then — only if the odour persists — deodorisation treatment. Never the reverse.

5. Cleaning from the bottom up

Deposits fall. If you start with the floors, you will redo them entirely after dealing with light fittings, tops of cabinets, door frames and air vents. The order is always: high level, then intermediate surfaces, then floors — floors last, once.

Three real jobs, and what they taught us

We are not a disaster restoration company and we do not pretend to be: on major losses we work alongside specialist restoration contractors rather than claiming to handle everything in house. We have, however, carried out a number of light to moderate post-smoke cleaning jobs once the fire service had made the premises safe. The three below come from building fires rather than wildfire fallout — but the material is the same: greasy soot and an odour that clings.

Flat after a kitchen fire — Paris 15th, 72 m²

An oil pan fire, contained to the kitchen, but smoke that travelled through the entire flat. Three technicians, one full day, around 18 labour hours. The hard part was not the burnt kitchen: it was the invisible film of soot covering every horizontal surface in the rest of the flat.

Office floor after electrical cabinet smoke — La Défense, ~450 m²

An electrical fault in the server room. Almost no fire damage, but smoke contamination across the entire floor plate. Two days on site. The difficulty was never the visible dirt: it was the burnt-plastic odour lodged in the suspended ceilings, the carpet and the return air grilles.

Common areas after a basement fire — Boulogne-Billancourt, ~300 m²

A fire in the underground car park, with smoke travelling up the stairwells. Scope: entrance hall, staircases, lift lobbies. The soot came off reasonably easily. The odour did not: several days of continuous ventilation were needed before residents noticed a real improvement. On this kind of job, patience is part of the method.

Step-by-step protocol for a home after evacuation

Order matters as much as method. Here is the sequence we apply, aligned with official health guidance, for a standard-sized home. Allow half a day with two people for a 60–80 m² flat, a full day for a house with outdoor areas.

Step 1 — Document before touching anything

Before any cleaning, photograph the deposits: window ledges, floors, garden furniture, textiles, appliances. Once cleaned, the damage can no longer be demonstrated. If you intend to file an insurance claim, those photographs are your only evidence, and they cost five minutes.

Step 2 — Air the premises, at length

Once the smoke has cleared, open every room wide, creating cross-ventilation, for at least thirty minutes before starting. Remove the damp cloths that were covering the air vents. Do not restart the ventilation system at this stage — that is handled at step 5.

Step 3 — Remove dry deposits without dispersing them

Visible ash accumulations are collected gently, by gloved hand or with a dampened piece of rigid card, then placed in a sealed bag. No broom, no feather duster, no compressed air. Removable textiles — curtains, rugs, covers, cushions — are rolled up without being shaken, carried out in closed bags, and washed separately from other laundry.

Step 4 — Clean with water, top to bottom

Light fittings, tops of cabinets and high furniture, door and window frames, skirting boards, then working surfaces, then floors. Damp wipes for objects and furniture, damp mop for floors. Rinse or change the water very frequently — as soon as it turns grey it is no longer cleaning, it is redistributing. Allow at least one bucket of clean water per room.

Step 5 — Treat the ventilation before restarting it

This is the step almost everyone skips. Remove and wash extract vents and air inlets, replace clogged filters, wipe the accessible interior of the grilles. Only then is the ventilation put back into service. A system restarted on a soot-loaded network will redistribute throughout the home exactly what you have just removed.

Step 6 — Flush the water and check outdoor areas

Run indoor taps for two minutes before drinking. Collect that water for cleaning. If you have a pool, check filtration and disinfection and skim out debris. Terraces, paths and garden furniture are rinsed with water, at low pressure, without a blower.

Offices and commercial premises

An office is not a large home. The volume of air moved, the presence of carpet, suspended ceilings, IT equipment and above all an air handling unit completely change the nature of the problem — and the order of priorities. It is also the only case with a hard deadline: reopening to staff.

Ventilation: the absolute priority, before anything else

In a commercial building, the air handling unit serves an entire floor plate. If it ran during the smoke episode, or if it is restarted without prior treatment, it will redistribute soot across every workstation within hours — including areas that had no deposit at all. The protocol is: keep it shut down, have the filters replaced by your HVAC maintenance provider, clean supply and return vents, and only then restart. Have it documented in writing: that is the question the labour inspectorate or the works council will ask if staff report respiratory discomfort on return.

Carpet, suspended ceilings and textiles: the traps

Carpet is a particle trap: it cannot be handled with a mop or a standard vacuum. It needs hot water extraction, or a certified HEPA vacuum worked slowly — never a standard office machine. Mineral-fibre ceiling tiles are porous and hold odour for a long time: in heavily exposed zones, replacing them is often cheaper than treating them, and more reliable. Acoustic screens and fabric chairs are treated last, after the ventilation and the floors.

IT, electrical and equipment

Fire soot is acidic and conductive. It does not merely soil: it corrodes contacts and circuit boards, and the damage often shows up weeks later. Rule of caution: do not mass-restart a visibly dusty IT estate, never blow compressed air over a workstation, and do not open the units. Exterior wiping with a damp cloth on powered-down, cooled equipment, yes. Internal cleaning, no — that is a specialist job, and it is usually covered by insurance.

Reopening: in what order

A clean reopening always follows the same sequence: ventilation treated and restarted, prolonged airing, cleaning of high level and surfaces, treatment of floors and textiles, flushing of all water points — taps, water fountains, plumbed coffee machines that have sat stagnant during closure — then a visual check before staff return. Tell your teams what has been done: in this kind of episode, anxiety comes far more often from silence than from the deposit itself.

When it stops being a cleaning job

Let us be clear: some of these situations are not a cleaning company's remit, and it is better to know that before starting than to discover it mid-job. Stop and call a post-disaster restoration specialist — or another trade — in the following cases:

• Materials burnt or were exposed to intense heat on site. That is no longer a deposit, it is fire damage, with a risk of structural weakening.
• The building predates 1997 and materials were degraded by heat. The risk of fibre release requires a survey before any intervention. Nothing is scraped, nothing is sanded.
• The fire service intervened with water: the premises must be dried before cleaning, otherwise mould develops within 48 to 72 hours.
• The odour persists after a full clean and ventilation treatment. That means the soot is lodged in porous materials or in the ductwork: it is a technical deodorisation job, not a cleaning one.
• A distribution board, technical cabinet or server is contaminated. Isolation and intervention by a qualified professional, never by a cleaning team. We never re-energise equipment exposed to smoke: that is a qualified electrician's job.
• A ceiling is unstable or the structure has been weakened. Evacuate, make safe, do not clean.
• Chemical contamination is suspected, or active mould has developed after prolonged water damage.
• The loss requires a forensic assessment before cleaning. The most common case, and the worst handled — see below.

The most common case: don't clean yet

We regularly ask clients not to start. Four situations mean waiting: the loss adjuster has not yet inspected; the origin of the fire is still under investigation; the soot may be needed as evidence; or no photographs have been taken. A single premature cleaning mistake can complicate a claim for a long time. It is frustrating, because the human reflex after a loss is to erase the traces as fast as possible — but it is the most profitable advice we can give.

What to prepare for the insurer

Three things, every time: time-stamped photographs taken before cleaning, a written description of the affected areas with the surface areas involved, and an itemised restoration quote. A single global "post-fire cleaning" figure is almost always challenged; a line-by-line quote — surfaces, carpet, ventilation, glazing, outdoor areas — goes through far more smoothly. We produce this type of itemised quote free of charge, whether or not you go on to instruct us.

What we can actually mobilise

To be concrete, here is the equipment held in stock and available without prior ordering.

• Vacuuming: 6 professional Class H HEPA-filtration vacuums, and 8 wet/dry vacuums.
• Dry soot: 120 to 150 dry chemical sponges in stock.
• Chemistry: around 80 litres of concentrated alkaline degreaser, over 100 litres of neutral detergent, over 500 microfibre cloths.
• Floors and textiles: 4 professional hot water extraction machines, 3 single-disc floor machines.
• Protection: around 400 FFP2 masks, 80 disposable coveralls, several thousand pairs of nitrile gloves.

Mobilisation times

For an emergency in Paris and the inner suburbs:

• Within 4 hours: 2 technicians.
• Within 24 hours: 4 to 6 technicians.
• Within 48 hours: up to 10 technicians depending on workload.

How we price it

Post-smoke cleaning is not priced like routine maintenance: the gap between a light deposit on smooth surfaces and greasy soot embedded in carpet is considerable. Our structure:

• On-site assessment: from €190 excl. VAT.
• Cleaning: generally €12 to €35 excl. VAT per m² depending on contamination level.
• Heavy degreasing: bespoke quotation.
• Weekend or same-day intervention: 25 to 50% surcharge.
• Insurance report and photographic documentation: optional, billed separately.

Summary table: the right action by area