The FROG uses air as the carrier gas and uses scrubber material (activated carbon and molecular sieve) to clean the air. The frequency at which these need to be replaced varies with how often the Frog is used and the cleanliness of the environment it is used in. For daily FROG use we recommend replacing the scrubber material every month, for weekly (or infrequent) FROG use, we recommend replacing the scrubber material every 3 months. Watch a video about how to replace the scrubber material.