In modern society, nearly all the people are familiar with air freshener. Air freshener is made from various kinds of ingredients including ethanol, aromatic chemicals, deionized water and so on. By sending out the fragrance, air freshener is able to cover up the bad smell, so as to alleviate the uncomfortable feeling caused by the undesirable odor. Air freshener is a chemical product which has been used in the field of environmental sanitation from the 20th century. There are two major components of air fresheners. The first component is deodorant, which generally includes propellants, condensed gases, and substances which can have chemical reaction with sulfur compounds, ammonia, amines, formaldehyde, such as ferrous sulfate. And the second component is freshener, which generally includes polyols, peppermint oil, essence and other substances. Air freshener has three major advantages. First of all, the price of air freshener is relatively very cheap. This is the most obvious advantage of air freshener. Generally speaking, most of the air fresheners sold in the current general cost between 15 to 30 Yuan, which is even cheaper than the car perfume. Secondly, air freshener is easy to use. Most of the commonly used air fresheners are gas-spray type, so it does not require any supporting facilities inside the car. Last but not the least, there are a variety of odor types for the consumers to choose from. For some drivers who like fragrance, especially women drivers, the good smell of air freshener is also one of the major reasons which attracts them to buy the air fresheners. Every coin has two sides, and this is the same with air freshener. There are mainly two defects of air freshener. The most obvious defect is that some ingredients contained in air freshener may bring potential harms to the human body. In the current market, there are many different types of air fresheners sold by different manufacturers, but most air fresheners are basically composed by such ingredients as ethy, aromatic chemicals, and so on. After these substances go through chemical decomposition in the air, they will produce some gases, some of which are air pollutants. As a result, this in fact exacerbates the degree of air pollution inside the car. As time goes on, it will exert an adverse stimulus on human body. In addition, the aromatic contained in air freshener will cause harms on the human nervous system, stimulate the respiratory tract of the children, and so on.