Best way to pre-kill?

[Raven01]

if you use gas, i would advise against the use of CO2.

its rather quick, but when mammals detect a CO2 increase in the blood stream they react with panic and a feeling of asphyxiation before they die.

i think its more humane to use a gas that prevent such a CO2 buildup.

nitrogen or helium is much slower, but since there is no CO2 buildup they fall asleep peacefully.

optimal would be nitrous oxide / laughing gas. super fast and super painless, it knocks them out within a few seconds and they feel euphoria. you can cheaply buy single-use cartridges that are usually used in whipped cream dispensers. its legal to own as long as you dont use it as a drug.

edit @ tribal: i think its the mass murderer clown from the Rob Zombie movie "house of 1000 corpses"

No they don't. CO2 was the standard accepted practice to euthanize rats when I was in university. We had no "kill chambers" just our rats in clear plastic bags and CO2 cylinders. The rats did not become agitated at all, they got dopey, went to sleep and then ceased breathing. Low doses are known to cause agitated/fearful behaviour but the high concentrations showed none of this despite what some people "think" with never having had experience using it.
If carbon monoxide were more stable it would likely replace CO2 very quickly though.

EDIT: OH crap I hadn't noticed there were 4 pages of this.