The air filtration system is the last line of defense of the biosecurity and epidemic prevention system in agriculture and animal husbandry. The gaseous pollutants in the pig house mainly include carbon dioxide, ammonia, hydrogen sulfide and dust particles. These substances are the cause of foul odors when they are mixed. Some research data show that the odor produced by manure is the product of the complex interaction of many single odor substances, and the source is related to the body odor of livestock and poultry, decaying and spoiled feed, and the anaerobic decomposition of manure in the house. In addition to controlling the source and reducing the generation of odor, the odor control measures are to control the spread of odor from the transmission route. At present, centralized ventilation and filtration systems are the most widely used solutions.