The question behind this one is usually whether the family can sleep in the room tonight. Usually yes.
The timeline
Modern water-based paints are largely odourless within two or three days, with the strongest smell in the first few hours. Oil-based products on trim take longer — up to a week in a closed room.
What actually helps
Air moving through, not just a window open. Two windows on opposite walls, or one window and a fan pointed outward, clears a room several times faster than a single opening.
What does not
Bowls of onion, coffee grounds, vinegar. They mask rather than remove, and the paint cures at the same rate regardless.
Low-VOC and zero-VOC
Genuinely better, widely available, and worth asking for if anyone in the house has asthma or if a nursery is being painted. The difference in cost is small and the difference on the first night is real.
When to be careful
Nurseries, bedrooms for anyone with respiratory problems, and rooms with no openable window. In those cases we plan around it rather than treating it as an afterthought.
Interior painting covers products and scheduling. Finished rooms are on our Facebook page.
