Once air for the brakes has been compressed by the locomotive's air pumps, it is distributed to the rest of the train cars—including the tender. On each car, the air is stored in pressurized steel canisters known … oddly … as brake cylinders (which must not be confused with the actuating cylinders attached to the brakes). It is these canisters that supply air for the actual braking work on each car, triggered when the locomotive engineer pulls the brake handle and reduces pressure throughout the air supply pipe that runs the full length of the train. These brake cylinders are designed to prevent leakage of air back into the train pipe, which would cause the rest of the brakes to release.