At present, there are three kinds of air conditioning filter elements for private cars, ordinary filter paper type filter element only has a filtering effect on larger particles of dust; some models are equipped with activated carbon filter, which can adsorb foreign substances and formaldehyde, but not specifically designed for viruses; some models are equipped with HEPA filter, which in principle can play a role in blocking viruses. If the car filter does not play any effect because of the spread between the people in the car. If a person drives and the road is empty, you can not wear a mask; if more than one person takes the car and passes through a crowded place, you need to wear a mask and turn on the internal circulation mode of the car’s air conditioner.