"...high concentrations of carbon monoxide, another deadly gas" could have been phrased rather differently given that this 'deadly gas' is essential for life on

"...high concentrations of carbon monoxide, another deadly gas" could have been phrased rather differently given that this 'deadly gas' is essential for life on earth at around >150ppm or so and without which almost all plants would die in short order never mind that respiration likewise for plants and animals involves its excretion along with water. There is no such thing as a single chemical substance that is <not> toxic for life forms at some concentration. Yes, there are optimum levels for all of them - in some cases down to almost zero.