This is Scientific American ― 60-Second Science. I'm Karen Hopkin.Need a quick breath check before your big meeting...or your big date?Well, scientists from South Korea may be able to help.They've engineered a portable device that detects even the tiniest trace of hydrogen sulfide...the stuff that smells like rotten eggs that is one of the primary offenders in oral obnoxiousness.Their work appears in the journal Analytical Chemistry.Bad breath, a.k.a. halitosis, can be more than a social inconvenience.A skunky mouth also may point to some serious underlying medical or dental issues."Early diagnosis is very significant to prolong your healthy life."Jun-Hwe Cha of the Korea Advanced Institute of Science and Technology.He says that most of the instruments used for diagnostics are found in clinics or hospitals...which may be tough to get to.And the electronic sensors that are currently used to sniff out various gases require a power source and precise calibration...not easy when you're out and about."So, we came up with a strategy to develop colorimetric gas sensors, which change its color when detecting biomarker gases."Think of it as a litmus test for your exhalation.To build their sensor, the researchers took lead acetate...a chemical used in some hair dye products that turns brown when exposed to hydrogen sulfide.And they embedded it in a three-dimensional nanofiber web...so the dye would spread out across a large surface area.That distribution gives the sensor the sensitivity it needs to detect trace amounts of H2S.