No it is actually using a dry ice cloud, based on CO2 deployment that high tech companies use to squelch fires. My husband works in one of those buildings, and when those gas jets release you get out or get dead. Your first gulp renders unconsciousness. You then asphyxiate within a minute.
With the dry ice method, you take a bucket, put dry ice in the bottom, pour hot water, wait for cloud to form placing lid on loosely (otherwise it will blow off). Once you have a nice cloud, lower bird into it. Putting some styrofoam on the bottom keeps the bird off the dry ice as a nicety. Close the lid. The bird takes a gulp, becomes unconscious, then dies fluttering from physical aftermath while asleep. It's over in about 20 to 30 seconds when done right.
The Amercian Veterinarian Association recommends CO2 for at home euthanasia. Birds are a little trickier as you have to use enough CO2 concentration due to the way their lungs function. CO2 has a bad name in the poultry industry because birds are ushered into a large building, then CO2 is slowly pumped into the building, which does cause a slow suffocation with panic in the birds.
But working on a small scale you are able to create a big cloud to lower the bird into (not safe for humans on a large scale). It is very effective and the kindest way I know of to cull.
LofMc