Should I buy a dehumidifier or air purifier for a musty basement?

If your basement smells musty, start with a dehumidifier.

A musty basement is usually a moisture problem first. Lowering humidity helps address the damp conditions that allow mold and mildew to develop. An air purifier can help with airborne particles and some odors, but it doesn’t reduce humidity or fix a damp basement.

Which should you choose?

• Choose a dehumidifier if: the basement feels damp, you see condensation on walls or windows, or there’s visible mold or mildew.
• Choose an air purifier if: the basement is already fairly dry but still has a lingering smell, or you mainly want to reduce dust, pet dander, and airborne particles.
• Use both if: the basement is damp and the smell is strong. The dehumidifier tackles the moisture problem, and the air purifier can help clean the air.

A couple of caveats

• A dehumidifier helps make the space less hospitable to mold, but it won’t guarantee mold can’t grow if there’s a hidden leak or ongoing moisture source.
• An air purifier may help with some odors and particles, but it’s not a substitute for removing the moisture source.

Before buying, check the basement’s humidity and look for leaks, seepage, or other sources of moisture. If humidity is high, a dehumidifier is the more important first step. If the basement is already dry and the smell remains, investigate the source and consider an air purifier as a supplement.