>CAPTAN is a fungicide (kills rot) used on fruit crops, and is added to gas
>to give it an odor.

        This is a confusion of a common or commercial name Captan for a
particular synthetic compound with the word MERCAPTAN (= thiol =
sulfhydryl) for a class of compounds containing the -SH pair of atoms.  It
is small molecules of this latter class that are added to natural gas and
LPG to assist leak detection by scent.  The proprietary fungicide Captan®
is not added to gas.

R