What is Relative Humidity?

What is Relative Humidity?


The environment in which an artefact is stored can affect the level of deterioration that occurs. Monitoring these environments can assist conservators in identifying any problem areas where collections may be at risk.

So first of all, what is Relative Humidity?

Humidity in general simply means that the air contains water vapour. So, if we say that the air is humid, it contains moisture, otherwise it is dry. But relative humidity gives the percentage of water vapour in the air for a particular temperature. It is defined as the ratio of the amount of water vapour present in the air to the amount of water vapour required to saturate it or the maximum amount of water vapour it can hold at that temperature. Relative humidity (RH) can change depending on the temperature; warm air holds more moisture than cold air.

So how does this affect artefacts?

Fluctuations in relative humidity can cause items to crack or split. Low RH can cause organic materials to become dry and brittle and if the RH is too high objects can become damp. This is when a build-up of mould can occur and insect pests can become a problem.

Each material requires its own specific environment so it is important to not only understand the optimum condition for your collection, but that you use accurate and reliable instrumentation to assist with environmental monitoring.

Our Hanwell ML4000 range of relative humidity and temperature data loggers and radio transmitters are well established within the heritage industry and are ideal for humidity in historic places such as museums and galleries.

Our range of humidifiers and dehumidifiers are also available to help monitor humidity levels within historic places.

For more information on a solution to suit you, please feel free to contact Cristina De Jesus our internal account manager for Heritage on c.dejesus@the-imcgroup.com or call 01462 688070 to discuss your requirements.