The regular wear of the sensor's own SO_X / NO_X filter leads over time to cross over time leads to cross-sensitivities of the CO sensor to gas components such as NO_X (nitrogen oxides) and/or SO_X (sulfur oxides). In the long term, this can quality of the measurement results in the long term.

With an external SO_X / NO_X filter, which can be easily connected between the gas conditioning unit and the gas connection nipple of the instrument, this effect can be and the gas connection nipple of the instrument, this effect can be effectively and inexpensively eliminated. After a color change of the granulate beads from purple-brown to gray-white, the granules are simply replaced.