As you can see in this photo, this homeowner is not protected by any crawl space door. Sealing all openings where outside air can get into your crawl space, is a major necessity. Once we've treated for mold and installed a dehumidifier, it's pointless if the crawl space is still exposed. You can never dehumidify a space that has exposed earth, outside ar leaking into it, or one that keeps leaking water.