The first step in getting rid of mold in a crawl space is removing the source of the mold. Mold spores cannot grow and thrive without moisture, so getting rid of any water leaks or similar problems should prevent mold from growing back. Next, you will need to remove any items which have been damaged or affected by the mold. Sometimes you may be able to get away with simply washing items in a water and bleach solution, but some things will need to be removed and replaced.
You may find mold in a crawl space if the area has been flooded during rain or if you have leaky pipes beneath the building. If pipes are the problem, you should fix them or have a plumber make any needed repairs. Flooding or leaking caused by rain water may not be entirely preventable, but you will probably be able to reduce the damage by sealing the entrance to the crawl space or installing a plastic piping system or ramp to divert water away from the building.
Once you have reduced the amount of moisture in the area, mold will likely lessen in severity since it needs moisture to live. To remove the remaining mold in a crawl space, you will need to clean or remove any affected areas. If insulation or other materials that cannot be scrubbed are infested, they will need to be removed completely. Drywall, brick, and other hard materials can be scrubbed using a bleach solution and water.
Before you get started, make sure that you wear a facial mask and gloves. Crawl spaces are generally very tight quarters and once mold spores are loosened it could be dangerous to breath them in. Wearing a mask will prevent mold inhalation, and you may consider wetting the area first to reduce their ability to travel through the air since water will weigh them down.
Be sure that any mold-covered items you remove are in an air tight bag or container to ensure that mold spores do not end up elsewhere in the crawl space or outdoors. Spores can land anywhere and in the right conditions, more mold may grow. Wipe the mold infested area down with bleach solution and scrub with a firm brush. Use a flashlight or headlamp to ensure that all spores have been removed.
Severe mold in a crawl space area may need to be handled by a professional. If you are unsure whether you will be able to effectively remove the mold without spreading the spores or causing further damage, do not attempt to treat the area yourself. Sometimes widespread infestation may require full replacement of all materials. This can be a costly endeavor but is necessary if certain dangerous mold varieties are present. Mold has been known to cause or aggravate certain conditions, such as asthma and bronchitis.