Frozen/Thawed mice and rats

How do they kill the f/t mice and rats? they say its more humane than it being strangled to death by a snake. But i just really want to know.

Most breeders use the CO2 method. They set up a chamber that is filled with CO2 gas, then add the mice. It is very fast, very painless and very clean. Basically the breathable air is removed and they pass out instantly. Some people worry about a buildup of CO2 in the mice, however I think if they sit out a little after there should be plenty of time for the gas to dissipate. Small ammounts of CO2 of course is harmless, but always do it in a well ventilated room and make sure to turn off your gas.

oh thanks. pleasant. lol