5.Do HCHs return moisture better than HMEs? Actually, all HCHs are HMEs. HCH stands for Hygroscopic Condenser Humidifier, while HME is the more generic term, Heat and Moisture Exchanger. All modern products that contain a special hygroscopic material to retain moisture in molecular form are considered HCHs. The only currently existing HME that is not an HCH due to the lack of a special hygroscopic material is a condenser humidifier, such as a pleated membrane HME. The use of hygroscopic salts, such as Lithium Chloride or Calcium Chloride further can enhance the performance of an HCH, but it is not a product requirement.