Reading a humidity spec: ±1% RH versus a single setpoint

A setpoint is not a control band

'70% RH' describes a target. It does not describe what happens when the room hits 95% in a monsoon week. A control band states the tolerance: ±1% RH means the chamber stays within one point either side, all year.

Test conditions matter more than the number

A humidor demonstrated at 22 °C in an air-conditioned showroom tells you little. Ask for a 72-hour empty-chamber test at 30 °C ambient, with the log supplied. That is the condition the unit will actually live in.

Bidirectional versus additive

An additive system (mist only) overshoots after a dry spell. A bidirectional system (mist plus desiccant-assisted drying) holds the band. If a specification only mentions humidification, it is half a system.

What to ask a supplier

Three questions: what is the control band, at what ambient temperature was it verified, and can I see the log. A supplier who cannot answer all three is quoting a number, not a system.