The complete guide to humidity monitoring

Humidity monitoring is the continuous measurement and recording of relative humidity, usually alongside temperature, in a controlled space such as a museum store, archive, laboratory, cleanroom, cold room or commercial building. Calibrated sensors log the data automatically at set intervals, raise alarms when readings drift outside defined limits, and store a time-stamped record. It replaces occasional spot checks with round-the-clock evidence that conditions stayed within specification, and an early warning the moment they do not.

Absolute humidity is the actual amount of water vapour in the air. Relative humidity is that amount expressed as a percentage of the most the air could hold at its current temperature, so it is the measure most monitoring uses because it relates directly to condensation, mould and material stress. Crucially, relative humidity changes as temperature changes even when the amount of moisture stays the same, which is why humidity and temperature are monitored together.

Unstable humidity causes damage in almost every controlled environment. Too high, and it drives mould, corrosion, condensation and the warping and cracking of organic materials such as paper, wood and canvas; too low, and materials dry out and become brittle. In regulated settings, relative humidity is often part of the specification that has to be evidenced. Continuous humidity monitoring catches swings as they happen, alarms a breach, and keeps a time-stamped record that proves conditions were controlled.

Look for sensors that measure relative humidity and temperature together; calibrated accuracy traceable to national standards, in the UK normally UKAS-accredited calibration to ISO/IEC 17025; continuous automatic logging rather than manual spot checks; real-time alarms that escalate by SMS, email and on-screen until acknowledged; a tamper-evident, time-stamped record with secure audit trails; coverage that scales across zones and sites; the option of both wired and wireless sensing; and a supplier that will support and recalibrate the system for years.

Most estates use both. Wireless sensors are battery-powered and quick to deploy where running cable is impractical, which matters in listed heritage buildings and busy occupied spaces, and they scale easily with repeaters. Wired sensing suits fixed positions where a permanent connection suits. Eltek’s GenII wireless transmitters measure relative humidity alongside temperature, and the wired GD10 is a built-in RH/T transmitter, both feeding one set of Darca software so you can match the sensing to each space.

Eltek uses one connected platform, Darca, in three layers. Collect measures relative humidity and temperature with battery-powered GenII wireless transmitters and the wired GD10 RH/T transmitter. Connect relays data securely from site to software through the SRV450 hub, with the SMS450 raising SMS alarms and repeaters extending range. Command provides live humidity and temperature dashboards, real-time alarms and compliance-ready reporting with full audit trails. Sensors carry UKAS-traceable calibration, and Eltek has designed and manufactured monitoring equipment in the UK for over 40 years.

There is no single correct figure; the right relative-humidity range depends on what you are protecting. Museums and archives typically hold collections within a stable band and watch the rate of change as closely as the absolute value, while laboratories, cleanrooms and commercial buildings each work to their own specification. The important thing is to set high and low limits appropriate to your environment, monitor against them continuously, and be alarmed the moment a reading drifts outside them. Eltek configures thresholds per site so each space is watched against the limits that matter to it.

Yes. Darca Command shows every site and zone in one view and lets you drill into any single sensor, so a team can watch relative humidity and temperature across several buildings or locations from one place. Connectivity through the SRV450 hub and repeaters that extend range across large, multi-zone and multi-building sites means the same platform scales from a single store or gallery to a whole estate, with role-based permissions keeping the right people in control at each site.