Dirt Crawl spaces have the high humidity levels necessary for mold growth. Humidity levels from 50-90% are easily found in dirt crawl spaces that have never flooded. Mold can grow on dirt, insulation, framing and even under your carpet on the first floor. Mold destroys organic materials as it feeds on them. Mold reproduces by producing millions of floating airborne spores, which some people are very sensitive to. Spores can be dormant for many years, waiting for the right conditions to grow. Some molds produce mycotoxins, such as the black mold Stachybotrys.