If your carpet got wet and didn’t dry out fully within 24 to 48 hours, there’s a good chance mold is already growing in the padding. That covers the obvious causes like flooding and burst pipes, plus the sneakier ones: an overwatered plant that’s been dripping for months, condensation pooling by a sliding door, or a swamp cooler pushing moisture into a room all summer with nowhere for it to go.
People here assume the dry air protects them. It doesn’t, because the water rarely comes from the air. Spring runoff off the Wasatch benches pushes through basement walls and under slabs. Ice dams back water up under the eaves in February and it runs down into the walls. Sprinkler lines and irrigation ditches in the older parts of town leak into crawlspaces for months before anyone catches it. Basement carpet is the usual casualty, and Mapleton has a lot of finished basements.
Watch for a musty smell cleaning won’t touch, dark patches on the surface, a damp feel underfoot, and allergy symptoms that only hit in carpeted rooms. If you can lift a corner and see staining or fuzzy growth on the backing, it’s well established. Don’t wait. Mold spreads, and once it’s into the subfloor, the fix gets far more expensive.