When something burns, a chemical reaction called combustion takes place. During combustion, the fuel (the thing that is burning) reacts with oxygen to produce carbon dioxide and water vapour. These two products are invisible gases. However, they are often accompanied by other substances, such as soot, ash, and unburned fuel particles. These substances are what we see as smoke.

The type of smoke that is produced depends on the fuel that is burning. For example, wood fires produce a white or grey smoke, while gasoline fires produce a black smoke. The colour of the smoke is due to the different types of particles that are suspended in the air.

Smoke can be harmful to our health. It can irritate our eyes, nose, and throat. It can also cause respiratory problems, such as asthma and bronchitis. In addition, smoke can contain harmful chemicals, such as benzene, formaldehyde, and carbon monoxide. These chemicals can cause cancer and other health problems.

For all of these reasons, it is important to avoid smoke whenever possible. If you are exposed to smoke, it is important to seek medical attention if you have any respiratory problems.