Is a dehumidifier or air purifier better for a musty room?

For a musty room, a dehumidifier is usually the better first choice because musty odors are often associated with excess moisture that can encourage mold and mildew.

An air purifier can still help, especially if it has a HEPA filter and activated carbon: it may reduce airborne particles, including some mold spores, and help with lingering odors. But it won’t fix the underlying dampness.

Which should you choose?

• Choose a dehumidifier if the room feels damp, clammy, or has condensation on the windows. Lowering humidity can make the space less favorable for mold and mildew.
• Choose an air purifier if the moisture problem is already addressed and you mainly want help with airborne particles or odors.
• Best overall: use both if needed — a dehumidifier to control humidity and an air purifier to help with particles and smells.

If the musty smell is coming from a leak, hidden water damage, or damp materials, those need to be repaired or removed too; otherwise the odor will likely return. And if there is visible mold, neither device removes it from surfaces — it needs to be cleaned up or remediated properly.