Full Name

ASTM E104 – Standard Practice for Maintaining Constant Relative Humidity by Means of Aqueous Solutions


This practice describes one method for generating constant relative humidity (RH) environments in relatively small containers.

This practice is applicable for obtaining constant relative humidity ranging from dryness to near saturation at temperatures spanning from 0 °C to 50 °C.

This practice is applicable for closed systems such as environmental conditioning containers and for the calibration of hygrometers.

This practice is not recommended for the generation of continuous (flowing) streams of constant humidity unless precautionary criteria are followed to ensure source stability.


constant relative humidity; RH; aqueous solution