Passive smoking, also known as secondhand smoke, occurs when non-smokers breathe in smoke from burning tobacco products, such as cigarettes or cigars, used by others. This smoke contains harmful chemicals that can affect anyone nearby, including children and pets. Exposure to passive smoking can lead to various health issues, including respiratory problems, heart disease, and an increased risk of lung cancer. It is especially dangerous for vulnerable groups, such as pregnant women and individuals with pre-existing health conditions, as they may experience more severe effects from inhaling secondhand smoke.