THE SHORT ANSWER
A reading is evidence—not a diagnosis.
Relative humidity shows how much water vapor the air holds compared with what it could hold at that temperature. The number changes with temperature, location, recent activity, weather, and HVAC operation.
One reading cannot confirm mold, find a hidden leak, identify an HVAC fault, or prove that you need a dehumidifier.
Return to the reading check →GENERAL RANGE
Use the number to choose the next check.
| Reading | What to do | What not to assume |
|---|---|---|
| 30–50% | Usually a useful indoor range. Keep watching if there are damp materials or other warning signs. | That the whole building is dry or problem-free. |
| 50–60% | Check again in a representative location and look for a repeating pattern. | That equipment is needed from one reading. |
| Above 60% | Investigate if it stays this high, especially with condensation, odor, staining, or wet materials. | That humidity alone identifies the source or confirms mold. |
EPA guidance recommends keeping indoor relative humidity below 60% and describes 30%–50% as ideal where practical. CDC guidance advises keeping it no higher than 50%. These are general moisture-control guides, not universal diagnostic thresholds.
MEASURE WELL
Record enough context to make the reading useful.
Place
Use a representative room location, away from direct sun, supply air, open doors, and recent steam.
Context
Record temperature, room, time, weather, and recent showering, cooking, laundry, or cleaning.
Pattern
Repeat the reading under comparable conditions and compare rooms before drawing a conclusion.
Physical signs
Active water, wet materials, staining, condensation, and unsafe access matter more than refining a sensor reading.
EVIDENCE BOUNDARY
What the evidence supports
Keep observing
The reading was brief, followed a normal activity, or has not repeated.
Investigate
The pattern repeats, affects several rooms, or appears with physical moisture evidence.
Get qualified help
There is contaminated water, electrical risk, structural concern, extensive wet material, unsafe access, or health symptoms.
This reference cannot inspect concealed damage, diagnose mold or HVAC faults, or choose equipment for a specific building.
Use the dashboard diagnostic →SELECTED SOURCES
Research behind the guidance
Fully Considered uses authoritative guidance to frame decisions and distinguishes general ranges from diagnosis. Product recommendations in the dashboard are based on documented specifications and decision fit, not hands-on testing.