This guide is general information, not medical advice. If you have health concerns, please consult a medical professional.
Why humidity matters
Humidity affects comfort, building materials and how easily mold can grow. Persistent high humidity allows moisture to collect on cool surfaces such as windows and exterior walls.
Aim for 30–50% relative humidity
The U.S. EPA recommends keeping indoor humidity below 60%, ideally 30–50%.
The suggested range
The EPA suggests keeping indoor relative humidity below 60%, ideally between 30% and 50%. Short spikes after showers or cooking are normal; sustained high readings are worth attention.
Below 60%, ideally 30–50%. It's the simplest number in home air health.
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Managing humidity
Run exhaust fans during and after showers and cooking, vent dryers outdoors, fix leaks, and consider a dehumidifier in damp rooms or crawlspaces. In coastal fog belts, ventilation and air circulation are especially helpful.
Room-by-room readings over several visits show where humidity is consistently higher than elsewhere.
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AirCare 365 provides humidity and mold and indoor air quality testing across the Bay Area.
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