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 non-flammable 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.
