Hydrogen sensing in humid air can not be assessed on the basis of concentration labels since the sensor surface is subjected to a mixture of hydrogen, oxygen, water vapor and purge gas flow. This study provides quantitative assessment of the catalytic plasmonic platinum nanodisk hydrogen sensor record in order to answer one research question: if the 80%RH and 80∘C operational conditions remain chemically well fed and analytically separable once they are translated into water feed mass, hydrogen dose, oxygen requirement, reaction-water formation, purge volume and detection floor margin. The sensor consists of a quasi-randomly distributed Pt nanodisk array deposited on fused silica with a mean disk diameter of 215 ± 10 nm, height of 25 nm and optical reference maximum of 710 nm. The operational record includes synthetic air with 20.5% oxygen concentration, total flow rate of 200 mL min−1, water feed rates of 0.081, 0.206 and 0.333 g h−1 at 20, 50 and 80%RH, hydrogen pulses ranging from 0.06 to 1.26 vol%, pulse intervals of 300 s, purges of 600 s, a 114 h humid core period within a 143 h stability run and detection floors of 30–50 ppm. One way of calculation is employed in all cases: water and hydrogen delivery is calculated based on the thermo-hygrometric dose transduction technique, and oxygen supply reserve, product water upper bounds and purge-to-dose separation are calculated by means of the co-reactant balance analysis technique. The 80%RH humid core is associated with the water mass of 37.96 g and carrier gas flow of 1368 L. Every 1.26 vol% hydrogen pulse requires 205 mL oxygen, but only 6.30 mL of oxygen are required for complete oxidation; thus the minimum oxygen reserve at the maximum dose equals 32.5. The water formed in reactions is small relative to the external water: 33.7 mg during ten pulses active period against 832.5 mg external water feed, 0.641 g during 114 h humid core period against 37.96 g external water. Hydrogen is programmed during 15.83 h, purge during 31.67 h and humid carrier flow outside pulse-purge blocks during 66.50 h of the humid core period. Calculated balances provide a direct answer to the research question: the selected humid operation conditions are unfavorable in terms of low water exposure, favorable in terms of high water throughput together with excess oxygen, small product water contribution, good purge volume separation and detection floors substantially lower than both the 600 ppm repeated pulse and the 1000 ppm comparison value.