Aluminum hydrazinium sulfate (AHS) double salt supported on sepiolite has been found to show good adsorption characteristics for acetalde. However, hydrazine is believed to be carcinogeric and is to be used with great care. This study, focused on thermal cracking characteristics of AHS adsorbent and showed that no emission of hydrazine was identified. The composition of emitted gases changed upon the adsorption of acetaldehyde, but it was estimated that hydrazine was easily, decomposed into nitrogen and ammonia before desorption from the support. From the amount of water generated during heat treatment, acetaldehyde is estimated to be in the form of acetaldazine when trapped on the adsorbent.