Controlled relative humidity environments are important for conditioning materials for shelf-life studies or for investigating the change in physical or dielectric properties after exposure.

The use of aqueous-glycerin solutions reduces the possibility of contamination of the materials or corrosion of electrode systems which would be more likely to result from saturated salt or acid water solutions.

Applicable material specifications should state the exposure conditions, including time, temperature and relative humidity, that a material should be subjected to before subsequent testing. Typical conditions are given in Practice D 618.

1.1 This practice describes a method for obtaining constant relative humidity ranging from 30 to 98% at temperatures ranging from 0 to 70°C in relatively small containers by means of an aqueous glycerin solution.

1.2 This practice is applicable for closed systems such as environmental conditioning containers.

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

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.