Smoke Damage in HVAC Ducts: What to Check

The smoke travels through the ducts during a fire, and the soot settles in them. Turn the air conditioning back on before the ducts are cleaned, and the soot spreads to every room in the house — including the rooms the fire never touched. This post explains what to check, why the vents stay sealed until the ducts are cleaned, and how the provider cleans them after a fire.

The second thing to understand is that the ducts are not a room. They are the highway the smoke travelled on, and the soot is in them the same way it is in the walls — except the ducts carry air, and the air carries the soot to every vent in the house. The provider seals the vents before cleaning, cleans the ducts, and treats them, so the soot does not spread to rooms that were not affected. If the ducts are not cleaned, the smell will come back every time the air conditioning runs.

How Smoke Gets into the Ducts

The smoke travels through the ducts during a fire, and the soot settles in them. The fire heats the air, the air rises, and the ducts carry it — through the vents, into the rooms, and back again. The soot settles on the inside of the ducts, on the vents, and on the filters, and it stays there until it is cleaned. A room that looks clean can still have soot in its ducts, because the ducts are where the smoke went.

The smoke gets into the ducts even when the air conditioning was off, because the ducts are open to the house and the smoke rises through them. The fire heats the air, the air rises through the vents, and the ducts carry it to the rooms above and the rooms beside the fire. The provider maps the ducts the same way the rooms are mapped, and the cleaning follows the map, not the eye.

The smoke also gets into the air handler, the blower, and the coils. The soot settles on the coils and the blower, and the smell comes back through the vents when the air conditioning is turned on. The provider checks the air handler first, because it is where the smoke is thickest, and the cleaning starts there. If the air handler is not cleaned, the soot will spread every time the system runs.

What to Check First

Check the vents. If the vents are blackened, if they smell, or if the filter is black, the ducts need cleaning. Do not turn on the air conditioning to test it — the test spreads the soot to every room in the house. The vents should stay sealed until the ducts are cleaned, and the air conditioning should stay off until the provider says otherwise.

Check the filter. The filter is the first thing the smoke hits, and it is the first thing that tells you how far the smoke went. A filter that is black is a filter that caught the soot, and a filter that is black is a filter that needs replacing. Do not reuse a filter that was in the house during a fire, and do not run the system without a filter, because the soot will go straight into the coils.

Check the rooms that look untouched. Smoke travels further than flames, and a room that looks clean can still carry a fine soot film and a smell that matters for the claim. The provider maps the smoke room by room, and the ducts are mapped the same way — and the cleaning follows the map, not the eye. Photograph every room before anything is moved or cleaned, because the photographs are the record your insurer will read.

Why the Vents Stay Sealed

The vents stay sealed because the ducts carry air, and the air carries the soot. Turn the air conditioning on before the ducts are cleaned, and the soot spreads to every room in the house — including the rooms the fire never touched. The vents are sealed with tape and plastic, and they stay sealed until the ducts are cleaned and treated.

The vents stay sealed because the soot is fine, acidic and persistent, and the particles are small enough to get into the lungs. The room should stay closed until the dry pass is done, and the ducts should stay sealed until they are cleaned. The provider seals the room, runs the air scrubber, and works in protective equipment — not because the soot is dramatic, but because it is fine, acidic and persistent.

The vents stay sealed because the smell comes back through them. The soot carries the smell, and the smell lingers in the ducts long after the soot is gone, and the smell is the last thing to go. The provider seals the vents before cleaning, cleans the ducts, and treats them, so the smell does not come back through the vents when the air conditioning is turned on.

How the Provider Cleans the Ducts

The provider seals the vents before cleaning, so the soot cannot spread to the rooms while the ducts are being cleaned. The ducts are cleaned with a HEPA vacuum and a brush, which lift the soot from the inside of the ducts without driving it deeper. The air handler is cleaned first, because it is where the smoke is thickest, and the cleaning starts there.

The provider cleans the ducts room by room, from the farthest smoke to the hearth, and each room is sealed once it is clean. The filter is replaced, the coils are cleaned, and the blower is cleaned, so the system does not spread the soot when it is turned back on. The provider will tell you what the cleaning found, and what still needs to be done, before the next step starts.

The provider treats the ducts after cleaning, so the smell cannot come back. The treatment neutralises the smell at the source, not a spray that masks it, and the treatment is applied after the cleaning, not before it. The smell is the last thing to go, and it is the thing that tells you whether the job is done. The provider will tell you when the ducts are clean, and will show you the readings.

When the System Can Run Again

The system can run again when the ducts are cleaned, the filter is replaced, and the air handler is clean. The provider will tell you when the system can run again, and will show you what was cleaned, because the record is what the claim is built on. The provider will not say the system can run before the ducts are cleaned, and the provider will not switch the power back on before the wiring has been checked.

The system can run again when the readings are normal. The moisture is read every day, and the walls are closed only when the readings say the moisture is normal — not when the surface feels dry, and not when the calendar says it is time. The readings decide, and the readings are what keep the job honest. The provider will show you the readings, because the readings are the record.

The system can run again when the smell is gone. The soot carries the smell, and the smell lingers in the ducts long after the soot is gone, and the smell is the last thing to go. The provider treats the source, not the smell, and the source is the soot in the ducts. The smell is the thing that tells you whether the job is done, and the provider will tell you when it is.

Smoke Damage in HVAC Ducts, in Order

1. Keep the system off — Do not turn on the air conditioning. The vents stay sealed until the ducts are cleaned.
2. Check the vents and filter — If the vents are blackened or the filter is black, the ducts need cleaning.
3. Call the provider — Call (561) 566-7293 and describe the smoke — where it is, how far it went, and whether the vents smell.
4. Seal and clean — The provider seals the vents, cleans the ducts with a HEPA vacuum and a brush, and treats them.
5. Replace the filter — The filter is replaced, the coils are cleaned, and the system runs again only when the provider says so.

Mistakes That Spread Smoke Through the Ducts

• Turning on the air conditioning before the ducts are cleaned
• Running the system without a filter, which lets soot go straight into the coils
• Reusing a filter that was in the house during the fire
• Cleaning the rooms but skipping the ducts
• Unsealing the vents before the ducts are treated

For help with this in Coachella, see Smoke & Soot Cleanup in Coachella — or go back to the Coachella fire damage restoration home page.