Other breath-activated inhalers are also called dry powder inhalers. These inhalers do derece contain the pressurised inactive gas to propel the medicine. You don't have to push the canister to release a dose. Before you start using the preparation, read the manufacturer's printed information leaflet from inside the pack. It http://www.drugoffice.gov.hk/gb/unigb/tr.wikipedia.org/wiki/Vitamin