What characterizes an open-circuit breathing apparatus?

An open-circuit breathing apparatus is characterized by its use of a compressed air cylinder that supplies fresh air to the user. In this system, the individual inhales clean air from the cylinder and, upon exhalation, releases the used air directly into the environment instead of recycling it. This design ensures that the user is continuously breathing in fresh, uncontaminated air, which is crucial in hazardous environments. Open-circuit systems are commonly used in firefighting and other emergency response situations, allowing for a reliable and safe air supply while avoiding the risks associated with rebreathing exhaled air.