Soot on Walls and Ceilingswhat it means and how to clean it

After a fire, soot on walls and ceilings is expected. It follows the path of hot smoke, so it is heaviest high on walls, across ceilings, above doorways and around vents. You may see a clean shape where a picture frame hung, because the frame protected the wall behind it.

Without a fire, soot can still appear. Scented candles, especially those with large or flickering flames, release soot that collects above where they burn. Wood-burning fireplaces that draft poorly push smoke into the room. Gas furnaces, water heaters and stoves that are out of adjustment can produce soot, and the U.S. Consumer Product Safety Commission notes that soot around a fuel-burning appliance can be a warning sign of a carbon monoxide problem. If you see soot near a gas appliance, stop using it and have it inspected.

Many Phoenix homes have knock-down or popcorn ceiling textures. Soot settles into the texture and is hard to remove without damaging it. Popcorn ceilings in homes built before the 1980s may contain asbestos, which the U.S. EPA says should not be disturbed without testing. If you have soot on an older textured ceiling, have it tested before cleaning or scraping.

Desert dust is another local factor. Fine dust settling with soot creates a gritty layer that scratches paint when wiped, so thorough HEPA vacuuming first matters more here.

If soot appears around a gas furnace, water heater, range or fireplace without any fire, treat it as a warning. Soot is a by-product of incomplete combustion, and the same conditions can produce carbon monoxide, an odorless gas that can cause illness and death. Stop using the appliance, ventilate, make sure your carbon monoxide alarms work, and have a qualified technician inspect it.

Common causes include a dirty or misadjusted burner, a blocked flue or vent, or a lack of combustion air because the appliance is in a closet that has been sealed up. Once the appliance is repaired, the soot can be cleaned using the methods in this guide.

Painting is often the last step after soot cleaning, and it is where many DIY jobs go wrong. Ordinary latex paint does not block stains or odor; soot shadows and smoke smell come through within weeks. The surface needs to be clean, dry and dull, then primed with a stain-blocking primer suited to smoke, commonly a shellac-based product.

Ceilings are the most demanding surface because soot collects there most heavily and light falls across them at an angle that shows every shadow. On textured ceilings, primer has to reach into every recess. If you see yellow or grey patches through fresh paint, the primer coat was too thin or residue remained, and the area needs cleaning and priming again.

Walls and ceilings are not the only surfaces soot reaches. Wood furniture and cabinets with a lacquer or varnish finish can usually be cleaned with a mild cleaner and soft cloth after loose soot is vacuumed, but acidic residue can cloud a finish if it sits for long. Chrome, brass and nickel fixtures can pit or tarnish and should be cleaned early. Unsealed wood, such as the inside of drawers, absorbs soot and odor and may need sealing. For anything valuable or antique, ask a professional before cleaning it yourself.

Small patches of light, dry soot can be a weekend job. After a fire, though, soot usually covers several rooms and mixes with oily residue, water and odor. Large areas, oily or smeared soot, textured or older ceilings, and soot that keeps reappearing are all signs to bring in professionals, who have HEPA equipment, respiratory protection and the right cleaners.