When the tobacco product is burned, two types of smokes are released: the mainstream smoke and the sidestream smoke. The mainstream smoke is the smoke that is first inhaled into the smoker's lungs and later released back into the surrounding air. Because of ample air supply that results in complete burning, its temperature could reach 950°C. The sidestream smoke is the smoke that curls up from the burning end of the cigarette. This smoke goes into the air before incompletely burned, resulting in a temperature of about 35O°C. The mainstream smoke makes up about 15% of second-hand smoke, the sidestream about 85%.

　　Based on chemical analysis, because of incomplete burning, the sidestream smoke contains more harmful gases and carcinogenic substances. Because the second-hand smoke is a combination of the mainstream and the sidestream smokes, it explains why the second-hand smoke is so poisonous. Therefore, when a smoker is smoking the cigarette, the people in the surrounding area are forced to inhale the smoke that fills the air, hence the name second-hand smoke, also known as passive smoking or non-voluntary smoking.

　　Basically, the mainstream and sidestream smokes have similar chemical composition, and they are the main source of indoor air pollution. Even though the second-hand smoke is diluted by air before it enters the human body, it still contains a large amount of harmful substances. Statistics show us that the number of deaths associated with second-hand smoke pollution is far greater than any other types of air pollution.

　　The amount of second-hand smoke a non-smoker is exposed to depends on the type of cigarette, the rate of smoking, the size of the room, the adequacy of ventilation, and time. Based on an experiment at Texas A&M University, a non-smoker's heart rate, blood pressure, and serum carbon monoxide level all increase dramatically when confined to a smoke-filled room for 30 minutes.

　　A research team at the University of Cincinnati Medical Center found that the smoke that is released when cigarette, pipe, or cigar is burned contains cadmium, which is harmful to the human body when inhaled. A research team at the Wayne State University in Detroit, Michigan found that the children who live in a household where the parents smoke are 200% more likely to have an acute illness (mostly respiratory) compared to the children from a smoke-free home.

　　Besides second-hand smoke, tobacco products are a major threat to the ecological system. The smoking ban on the beaches in Los Angeles, California was enacted because every year there was several tons of cigarette butts thrown by the visitors to the beach. The nicotine and other harmful substances in the cigarette butts will eventually enter the sand and the ocean, damaging the ecological system of the beach and the ocean. The smoking ban will give back to the public a 21-kilometer long beach that is free from pollution.

　　Smoking is not only harmful to the human health, the littered cigarette butts are a eyesore for the cityscape. The Hsinchu City Bureau of Environment Protection reported during a meeting at the Environmental Protection Administration that, because there are lots of littered cigarette butts on the streets, the cost to clean up went up drastically. They suggested to collect a "tobacco product clean-up fee", to be charged to the tobacco companies and smokers. The money will be used to clean up the streets throughout the region.

　　Therefore, from now on, if you are asked the question, "Do you mind if I smoke?" be sure to say, "Yes, I mind. It is harmful to my health". Don't be afraid or embarrassed to say no to other people, because their actions have polluted the air we breathe, and they are taking others' health away. The smokers need to quit smoking as early as possible so they don't produce any more second-hand smoke for the people around them.