"Too bad there's no such thing as a real "harmless sleep gas," like what you see in all the movies. Would be very useful for many police and military situations."

If they could "gasify" benzodiazepines it might be possible. That's the class of drug which includes Valium, Librium, Xanax, Versed, Ativan, etc.
Those sedate without depressing breathing or ultimately stopping the heart. Might as well save them and beat yourself to death with a sack of 'em as swallow 'em to try to commit suicide. (In combination with other drugs they are very lethal, but not usually by themselves.)

The way an overdose of narcotics work is that they first make one sleepy, then depress the breathing. People go to sleep and forget to breathe. Very dangerous, breathing is more than just "nice".

One advantage of inhalants is that they act fast and are usually gone as fast as they act. Any of those drugs, though, are hard on folks in marginal condition.

I think you're right, it would solve a lot of problems if there were some non-lethal colorless, odorless, fast-acting "sleeping" gas which doesn't absolutely ruin a liver.

Arf