A standard humidity system is designed to enable temporary operation down to -10°C dew point. A low humidity option will enable extended operation down to 5 grains of moisture per pound of dry air minimum limitation and humidity range from 5% RH to 98% RH.
The low humidity option incorporates a dry air purge for ultra low dew points. It also adds a bubbler humidity system which allows small amounts of moisture to be added to the air for low humidity control. This eliminates problems associated with adding hot steam to a cold environment which creates two problems: heat that needs to be taken out of the system and steam generator oscillation.