The stability of the surrounding environment is a vital and basic factor in the preservation of art, requiring temperature and humidity to be strictly controlled.

Fluctuations in temperature and humidity caused by external factors, such as the weather or the number of visitors, are a major problem for museums.

Fluctuations that occur repeatedly over a short period of time will have the most damaging effect as the materials do not have enough time to acclimatise. For example, an influx of people at one time will increase the humidity considerably, especially on a rainy day.

These effects may be very visible such as materials warping, splitting or cracking or they can be microscopic but over time will become more obvious. As works of art grow older they become brittle and fragile, and less able to readjust their internal moisture level without damage.

Museums need to control the environment around exhibits 24/7, as temperature and relative humidity can fluctuate frequently and dramatically on a daily basis. This requires constant operation of the humidification system, which therefore needs to be reliable and responsive.