The smell of fresh paint is solvent vapor, and whether that vapor can ignite depends entirely on what's in the can. It's a question worth getting right before you close the windows and turn on the furnace.
Fumes from oil based paint, alkyd paint, shellac primer, lacquer, and paint thinner are flammable. In a closed room those vapors can build to a concentration that a pilot light, a water heater, a space heater, or the spark from a light switch will ignite. Fumes from latex and acrylic water based paints are not flammable, though they are still worth ventilating.
Which Paint Fumes Burn
| Product | Solvent | Fumes flammable? |
|---|---|---|
| Latex / acrylic wall paint | Water | No |
| Oil based / alkyd paint | Mineral spirits | Yes |
| Shellac based primer (BIN) | Denatured alcohol | Yes, very |
| Lacquer, lacquer thinner | Acetone, toluene, xylene | Yes, very |
| Spray paint | Acetone plus propane/butane propellant | Yes, very |
| Paint thinner, mineral spirits, turpentine | Itself | Yes |
How Paint Fume Flash Fires Happen
Solvent vapor is heavier than air. In a closed room it pools near the floor and drifts through doorways, and it only needs to reach about 1 percent concentration for some solvents to be within their flammable range. The ignition sources are the ones people forget are there: the water heater pilot in the utility closet, the furnace cycling on, a space heater in the next room, a light switch, a power tool. The classic case is someone refinishing a floor with lacquer or shellac in a closed house with the furnace running. Those fires start with a flash that fills the room.
Ventilating Safely
- Open windows on two sides of the space for cross ventilation, and put a box fan in a window blowing out.
- Turn off pilot lights and set the furnace and water heater to off or vacation mode when using oil based, shellac, or lacquer products indoors.
- Don't run the HVAC fan; it carries vapor to every room with a spark source.
- Keep cans closed when you aren't pouring from them. Open cans are the main vapor source.
- No smoking, no candles, no open flame anywhere in the house.
- Keep ventilating for at least a day after finishing. Solvent based finishes keep releasing vapor as they cure.
Are the Fumes Toxic Too?
Yes. Even nonflammable latex fumes contain VOCs that cause headaches and irritation. Solvent fumes are worse: dizziness, nausea, and at high concentrations, unconsciousness. If you feel lightheaded, get outside. Low VOC latex is the easy answer for most interior painting.
Related reading: is paint flammable, is spray paint flammable, and is latex paint flammable.
