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Quick Answer
If you are preventing mold, start with humidity control. If you are improving air quality after mold was present, use an air purifier. Many homes benefit from both.
Target indoor humidity around 30 to 50 percent. See our guide to humidity control.
What a Dehumidifier Does
Dehumidifiers remove moisture from the air, making it harder for mold to grow. They are most effective in damp basements, crawlspaces, and rooms with poor ventilation.
- Reduces moisture that fuels mold growth
- Best for damp or below grade areas
- Prevention focused rather than cleanup
What an Air Purifier Does
Air purifiers with true HEPA filters capture airborne mold spores, dust, and allergens. They do not remove moisture or stop mold growth on surfaces.
- Reduces airborne spores and particles
- Helpful during remediation or after cleanup
- Does not address moisture or hidden growth
Learn more about airborne mold and how to interpret indoor results.
Which One You Need
Choose a Dehumidifier
- You have musty odors or damp air
- Basement or crawlspace feels humid
- Condensation forms on windows
- Humidity stays above 60 percent
Choose an Air Purifier
- You want to reduce airborne spores
- You are sensitive to allergens
- You want cleaner air after remediation
- You need a temporary solution while fixing moisture
When to Use Both
In many homes, the best approach is a combination: control moisture with a dehumidifier and clean the air with a HEPA purifier. This is especially useful during remediation or in humid climates.
Pairing both tools does not replace fixing leaks or water damage. See our guide on what to do after a leak.
Sizing and Placement
- Dehumidifier size should match room or basement square footage
- Place dehumidifiers near the moisture source and allow airflow
- Air purifiers should be sized for room volume and run continuously
- Replace filters and clean coils on schedule