Testifire's CO stimulus is unique because, unlike pressurised CO canisters, the CO is generated on demand from activated carbon supplied in capsule form with no pressure or stored CO. The number of tests from a capsule is dictated by the response time of the detectors under test and can range between 50 and 150 tests. Although there is much more to the comparison than material cost, typically this equates to between four and eight times that produced by an aerosol.
Other reference : 517.001.238, RE8-CO