Feeder Euthanasia the Easy Way, and Humane too...

[elevatethis]

Would putting the dry ice in the cooler before putting the rats in, make a difference?

Yes! Exposure to a high concentration of CO2 can actually be painful and cause respitory distress. If you allow the buildup to gradually increase, it is an anesthetic at low concentrations, and by the time the CO2 builds up to a deadly concentration, the rats are in La-La Land.