There are a few different benefits to crawl space air vent covers. These air ducts allow homeowners and business owners to improve the indoor air quality of their homes and businesses. It is important for people to know that mold can grow in crawl spaces even if the vents are closed. If this is not taken care of, then the mold can become a serious health problem. Sometimes these air vent covers are referred to as crawl space dehumidifiers. The only difference between these and your regular air conditioning unit is that it is set up to humidify the air in your home. There are also many of these covers that come with a mesh cover to help keep the moisture out as well. Your crawl space cover is going to be able to take care of most of the moisture problems that occur in your home.