A poultry stun detection system is designed for using with a poultry slaughter platform, wherein the poultry stunning detection system includes at least: a first camera device, a second camera device, a network transmission device, and a computer processing device. The poultry stun detection system utilizes visual devices to immediately determine whether the stunned poultry still has perception in real time, and employs the YOLOv4 deep learning model to enhance the recognition accuracy of whether the poultry has lost its consciousness after stunning.

A method of reducing stress level in animals such as pigs may include: sealable enclosing the animals in at least one chamber; exposing the animals to a gas mixture comprising oxygen and at least one type of physiologically inert gas; gradually decreasing the oxygen concentration from a maximum level, to a minimum level; gradually increasing the at least one physiologically inert gas concentration from a minimum level to a maximum level; wherein the minimum level of the oxygen concentration is higher than the anaesthetic causing concentration for the animals.

A method for processing a live fish can include: determining a set of fish attributes of a fish, optionally sorting the fish based on the set of fish attributes, euthanizing the fish, exsanguinating the fish, and/or any other suitable steps. In variants, the method can additionally or alternatively include: discarding the fish after sorting, further processing the fish, and/or tracking the fish. However, the method can additionally and/or alternatively include any other suitable elements.

A method for supplying CO.sub.2 gas to a site comprising a facility (20) that requires CO.sub.2 or a mixture comprising CO.sub.2, such as an abattoir or a greenhouse for cultivating plants, comprises the following steps: a boiler (4) capable of supplying hot water to the site is arranged within the site, the boiler carrying out the process of oxycombustion between a fuel (14) and pure oxygen (1), the oxygen that supplies the boiler being obtained from a liquid oxygen source present on the site; and some or all of the CO.sub.2 contained in the flue gas produced by the boiler is recovered by transferring heat between the flue gas and the liquid oxygen in an exchanger (2).