To test for mold in a house, start by using your senses: look for visible patches of black, green, or white growth, especially in damp areas like bathrooms, basements, and under sinks, and sniff for musty odors. For a DIY test, you can buy a mold testing kit from a hardware store; these often include a petri dish to expose to the air for 48 hours. If you confirm growth, it's better to hire a professional for identification and safe removal, as some molds are toxic and require special handling. how to test for mold in a house 38