Okay! I think you’re onto something, here! "Trace gasses" cannot possibly harm anyone!
So let’s put you in a room with the equivalent amount of the "trace gas" hydrogen sulfide—400ppm.
First, you’ll notice the strong characteristic stench of rotten eggs, but at 400ppm, that will quickly pass within just a few breaths, as the olfactory nerve is attacked and permanently destroyed.
So, the rotten egg smell is gone, and you’re thinking nothing is wrong—sorta like how you feel when a record-breaking heat wave passes. But now, the "trace gas" is attacking your optic nerve, and you have perhaps five or ten minutes to get out of there before you are blind.
After wandering around in the dark for a few more minutes, you’re starting to have difficulty breathing, as your lungs begin to fill with fluid. Your heart begins pounding from the lack of oxygen.
"But how could this be?" you ask yourself, "There’s only 400ppm in here; there should be plenty of oxygen!"
But as you’ve shown with your comment above, you don’t consider secondary and tertiary effects. You begin to get a severe, brain-splitting headache within a half-hour, and you start getting sleepy. Maybe if you just lie down and ignore it, it will all go away!
Several hours later, someone thinks to check on you, and they haul your lifeless body to the morgue, where the coroner declares, "Hey, this one died of stupidity!"
All due to a little "trace gas…" "Insignificant by definition."