Relative humidity
Relative humidity is how much moisture the air holds compared with the most it could hold at that temperature. Too dry and airways, skin and eyes suffer; too damp and mould, dust mites and condensation take hold. A mid-range band keeps people comfortable and the building healthy.
The band that protects people and buildings.
Humidity sits in a healthy middle. Stray too far either way and you trade comfort for irritation, infection risk or material damage.
Airways & infection
Very dry air irritates airways and lets some viruses survive longer; the mid-range band is easiest on people and least friendly to pathogens.
Mould & damp
Sustained humidity above ~60% invites mould, dust mites and condensation — a health hazard and a building-fabric problem.
Materials & preservation
Wood, paper, electronics and sterile goods all have a moisture comfort zone. Stable RH protects stock, equipment and archives.
Comfort
Humidity shapes how warm or clammy a room feels. The right band makes a given temperature feel comfortable rather than stuffy.
Aim for the middle, not the extremes.
Like temperature, humidity has a healthy band rather than a single ceiling. Both ends carry a cost — dryness on one side, damp and mould on the other.
Where the moisture comes from.
Indoor humidity is a balance of moisture added inside and moisture carried in or out by ventilation and the weather.
People & activity
Breathing, washing, cooking and cleaning all add moisture. Busy, crowded rooms trend damper.
Ventilation
Fresh air dilutes or adds moisture depending on outdoor conditions. Too little traps damp; too much can over-dry in winter.
Heating & cooling
Warming air lowers relative humidity; cooling raises it. HVAC strategy strongly shapes the reading.
Building & leaks
Damp ingress, leaks and cold surfaces create local high-humidity pockets where mould starts.