Condensation of the water vapour will not occur, even when the relative humidity approaches 100% providing the air temperature remains constant. So the risk of condensation (and therefore corrosion) arise mainly because of large drops in the air temperature, where at new lower temperature, the volume of water vapour is too much for the air to hold.Special attention needs to place where
- Variation between daytime and night-time reaches 20ºC to 30ºC
- Seasonal temperature variations are large
- Temperature variation occur due to the intermittent functioning of encased apparatus such as electrical conductors and resistors, fuses, circuit breakers or relay motors, which release calories when in use
- The greatest risk of condensation is in high humidity environment, where a drop of just 5o C will on average cause water vapour to condense
As a general rule it is enough to maintain relative humidity of enclosed air below 30% to avoid risk of condensation.