Detection of oxygen traces in nitrogen- and hydrogen-rich atmosphere

Tin oxide sensors are evaluated to detect traces of oxygen in the range 0–100 ppm both in nitrogen and hydrogen (4.5 vol% H2 in N2) atmospheres. In nitrogen, significant relative responses to oxygen are measured at 623 K and 723 K. However, at lower temperature, 523 K, the response strongly decreases. In the presence of hydrogen, on the contrary, interesting responses are measured at 523 K. At higher temperature, 623 K and 723 K, on one hand SnO2 sensors begin to reduce, and on the other hand, oxygen is partly consumed by reaction with hydrogen. Oxygen trace detection (5–100 ppm) is thus only possible in hydrogen atmosphere (4.5 vol% H2) at 523 K.