Moisture in the crawl space is a magnet for spiders, mice, rats, snakes, termites and other nasty pests. Because the crawl space is usually left undisturbed, this provides a safe haven for critters looking for a cozy home. What's more, much like our kids, critters don't usually clean up after themselves. Pathogens from rodent droppings ad urine can affect the air quality inside your home.