I don't know if it's gas from the latest volcanic activity on Earth or/and the effect of the solar storm/solar radiation on the latest Siberian and Canadian wildfire smoke that has accumulated there due to some sort of atmospheric trap (quite a bit of it has been blown into the Arctic Ocean over the last few months). But the concentrations are, yes, pretty deadly if it is indeed a tropospheric phenomenon. What if it lands on the ground?

The CO level is just impossible as 10 000 ppbv