What is simple asphyxiant?

Answer 1

A simple asphyxiant is a non-toxic or very mildly toxic and (mostly) inert gas which works by simply displacing oxygen in the lungs. Nitrogen, which makes up almost 80% of the Earth's atmosphere, is itself a simple asphyxiant, but it's mixed with plenty of oxygen in the atmosphere for us to breathe, and it's at this roughly 4:1 ratio of nitrogen to oxygen to which we are best-adapted as a species.

Other simple asphyxiants include helium, argon and xenon. Helium, as you probably know, is often inhaled to lower the pitch of the voice for comic effect. Doing so in periods of a few seconds each, with time in between to refill the lungs with adequate air, is perfectly harmless. However, if you were to breathe nothing but helium, you would eventually fall unconscious, and potentially stop breathing (so even if you were to fall unconscious from inhaling helium from a balloon, there's no guarantee you'll start breathing the normal air of the room again). A few minutes of that, and irreversible brain damage occurs. A few minutes more, and you're dead. So never do this by yourself and always err on the cautious side-the mechanism which triggers the feeling of suffocating is a lack of carbon dioxide, *not* a lack of oxygen, so you may not realize you are being asphyxiated until it is too late. Never underestimate an asphyxiant. Some asphyxiant gases do have other effects. Xenon, for example, is a powerful anesthetic and can produce unconsciousness rather quickly in high concentrations. It also produces the opposite effect of helium on the voice, lowering instead of raising the pitch, but this shouldn't be done because of its anesthetizing effect.

Some gases, like hydrogen, are also non-toxic and can asphyxiate in the same way, but aren't considered simple asphyxiants because of their reactive qualities (i.e., they are not inert).

Simple asphyxiants are not technically toxic, or are only very mildly toxic, which is why breathing them in this way is otherwise harmless. Asphyxiants are most easily understood when you know what a toxic gas is-an asphyxiant is really just any non-toxic gas that is not oxygen. Toxic gases are far more dangerous, and breathing them can cause damage and death even if you were to refill your lungs with enough air each time. A well-known example of a toxic gas is carbon monoxide (CO), which bonds with hemoglobin (the oxygen carriers in red blood cells) to form carboxyhemoglobin, which prevents that hemoglobin from transporting oxygen (it's carrying the CO instead). Even if there's lots of oxygen mixed with the carbon monoxide, CO bonds more readily to the hemoglobin than the oxygen, so there will never be enough oxygen being carried in your blood, even if there's plenty in your lungs. Even low concentrations of carbon monoxide can cause poisoning and death.

That might be more than you were looking for, but it's important to recognize the difference between an asphyxiant gas and a toxic gas.