There are three ways to test the air in your home: consumer air-quality monitors, standard single-target tests (like a mold or radon kit), and professional Advanced Indoor Air Quality testing. Each answers a different question — and knowing which one you need saves money and worry. Start with the signs Your home usually tells you when the air is off: allergy or asthma symptoms that ease when you leave, musty odors you can't locate, condensation on windows, dust that returns o