Hydrogen sulfide (H2
S) is a malodorous, very poisonous, and flammable gas. It can be detected as SO2
using fluorescence after conversion using a hot catalyst. This technique is well established and as such also recommended by authorities such as the EPA. Our paper describes how at a relative humidity as low as 5 %, significant amounts of H2
S pass the instrument undetected. At ambient levels of relative humidity, up to 1/3 of all H2
S passes the instrument unnoticed.