What is Relative Humidity?

Relative Humidity

What is Relative Humidity?


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

How does this affect artifacts?

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 mold 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.

We’ve got 10% off all new orders of selected data loggers when you quote the code Logger10*

For more information on a solution to suit you, contact our VP of Business Development, Meredith Paetz by emailing meredith@hanwell.com or call (757) 213-6841 to discuss your requirements.

*Offer valid until 31st July 2019 and only available for new orders.