In various embodiments, rapid, sensitive detection of molecular hydrogen is achieved by in a detector that divides sample gas into two flows by dividing the sample gas before dampening variation and converting hydrogen to water vapor at two different points. For example, a detector may receive sample gas that includes ambient water vapor and hydrogen, divide the sample gas into a chemical conversion flow and bypass flow, perform a first chemical conversion of hydrogen in the chemical conversion flow to water vapor, alternate between drying the converted chemical conversion flow or the bypass flow to produce a modulated flow, perform a second chemical conversion of hydrogen in the modulated flow to water vapor, measure water vapor in the converted modulated flow to produce a water vapor signal, separate the water vapor signal in the time domain to extract a hydrogen-derived water vapor signal, and output a hydrogen signal based thereon.

In various embodiments, rapid, sensitive detection of molecular hydrogen is achieved by in a detector that divides sample gas into two flows by dividing the sample gas before dampening variation and converting hydrogen to water vapor at two different points. For example, a detector may receive sample gas that includes ambient water vapor and hydrogen, divide the sample gas into a chemical conversion flow and bypass flow, perform a first chemical conversion of hydrogen in the chemical conversion flow to water vapor, alternate between drying the converted chemical conversion flow or the bypass flow to produce a modulated flow, perform a second chemical conversion of hydrogen in the modulated flow to water vapor, measure water vapor in the converted modulated flow to produce a water vapor signal, separate the water vapor signal in the time domain to extract a hydrogen-derived water vapor signal, and output a hydrogen signal based thereon.