Carpet needs to dry out within 24 to 48 hours of getting wet. If it doesn’t, mold is almost certainly already in the padding. The obvious culprits are flooding and burst pipes, but plenty of jobs we see come from quieter problems — a potted plant that’s been slowly dripping for months, condensation collecting under a sliding door, or a closed room where the marine layer humidity just sat. Santa Ana’s older neighborhoods are particularly prone to this. A lot of the housing stock here was built in the 50s and 60s on slab foundations with no real moisture barrier underneath, so ground-floor carpet doesn’t have much protection.
The signs to watch: a musty smell that won’t clean out, dark patches you can see on the surface, a slightly damp feel when you walk on it, or allergy symptoms that seem to only show up in carpeted rooms. Lift a corner of the carpet — if the backing is stained or has visible growth, it’s been there a while. At that point, don’t wait around. Mold works its way into the subfloor, and once it does, you’re in a different price bracket.