In the euthanasia chamber setup, a CO2 cylinder is connected via tubing to one end (Lower End) of a flow controller, while the other end of the flow controller (Upper End) is connected to the Upper nozzle of the chamber. The chamber is designed to be airtight. When the user initiates CO2 flow using the flow controller, the density of CO2 is being higher than that of oxygen (O2), results in CO2 filling the chamber from the bottom to the top. This directional flow ensures that CO2 is first introduced into the lower portion of the chamber and gradually fills upward.