Suffocating in breathable air

it clearly sais in the tooltip, that the pressure is too low to be breathable. as you dug up you caused sand to fall down and block the flow of breathable oxygen, of course your dupe suffocates. try breathe in a sealed room without air

The dupe was suffocating before the sand fell down

still, air pressure is too low to breathe. gases do not flood the rooms as fast as they wood irl.

maybe the air shouldn't the color that is "breathable" - according to the legend on the right

that's true. they seem to be unsure whether to use the colors to signal the breathability in general or to color the different gases. so in this case it is dark blue because it is still oxygen and therefor "breathable" in general even if it is "unbreathable" because of low pressure. they would have to change the color of hydrogen to red, because at this time it is used for the color for "barely breathable". they also would have to change contaminated oxygen to green or something because it may be "toxic", but it is still "breathable"... they should overthink their color overlay and i guess they will at some point.

This is an old bug report, but it is still open, so...

I have a base of 45 duplicants.  It is well oxygenated across the whole interior, but a duplicant just suffocated to death in the middle of the base where there was 2000 g of O2 per tile (except the standard CO2 that floats around.  Occasionally, I see them suffocate in the bathroom, could going to the bathroom be a higher priority than breathing?  If so, that seems like a bit of a mistake in the list of priorities.