Humans don’t breathe in standard ways. They are not a pure sine wave, in and out evenly. The inhale may be rapid and then a long slow exhale. Older style breathing simulators cannot achieve this variation, being mechanically driven pistons. With a computer controlled drive system, the wave form can be any shape required. It can be repeated endlessly, on demand.
If true human breathing simulation is required, then recording an human’s actual breathing pattern is required. The machine can then reproduce that recording as required. Again, with a computer controlled, infinitely flexible drive system this can be reproduced on demand.