The most common indoor air pollutants are things such as mold, cooking odors, cooking smoke, lead particles, asbestos, carbon monoxide, nitrogen dioxide and even radon.
Some pollutants indoors you can see and smell while other pollutants such as carbon monoxide and radon are silent and have no smell.
If you do start getting headaches or feeling dizzy then you could have carbon monoxide building up in your house.
If that is the case get outside and call 911.
Carbon monoxide can easily kill you and fast and is a common way people die in their sleep.
Have a carbon monoxide detector in your home to detect any carbon monoxide and make sure gas vents to heaters and furnaces, water heaters etc are all vented properly.
Second hand smoke is also another common indoor air pollutant.