A Halimeter is an instrument for measurement of the level of volatile sulfur compounds (VSCs) in the mouth.
The instrument measures parts per billion levels of hydrogen sulfide and, to a lesser extent, methyl mercaptan, two gases which were previously shown to be associated with bad breath using gas chromatograph by Dr. Joseph Tonzetich in the late 1960s.
The Halimeter is manufactured by Interscan Corp. in California, and based on their earlier model 1170 portable sulfide monitor.
[1][2] These studies, conducted for the first time by Dr. Mel Rosenberg, showed a significant correlation between monitor levels and oral malodor scores.
The small size, simplicity of use, and price (relative to gas chromatograph) of the Halimeter made it popular among dentists seeking to diagnose and treat bad breath, as well as scientific researchers.