Find and fix any water leaks
Improve ventilation with fans or open windows
Use a dehumidifier to keep humidity low
Clean and dry any damp surfaces
Remove mold and mildew with appropriate cleaners
Wash or replace musty carpets, rugs, and fabrics
Dispose of rotten cardboard, paper, and other absorbent items
Check and clean drains, sump pumps, and floor drains
Seal cracks in walls and floors
Store items in sealed plastic bins instead of cardboard boxes
Use odor absorbers like baking soda or activated charcoal
Clean gutters and improve exterior drainage
Inspect for sewage or plumbing issues
Replace HVAC filters if the basement is connected to the system
Keep basement humidity below 50 percent
Call a professional if the smell persists or mold is extensive