Soffiante e tirafumo
La quantità di ossigeno presente nell'aria determina l'intensità con cui il combustibile brucia e, di conseguenza, la temperatura all'interno del forno della locomotiva a vapore.
The most basic way the air gets fed into the firebox is simply by draft from opening the regulator and propelling the vehicle. As the steam from the cylinders is expelled through the blastpipe, it draws fresh air into the firebox with every cycle. The higher the cutoff setting the higher the draft.
Inoltre sono presenti due meccanismi di controllo progettati per regolare il tiraggio, ovvero il soffiante e il tirafumo.
Blower is usually operated by a valve. When open, it releases steam from the boiler around the chimney area. This creates draft, bringing more air into the firebox. This is used when there is a desire to increase the temperature of the firebox, but not to accelerate, such as in the case of going downhill or being stationary. Having the blower open while accelerating is wasteful however, because the acceleration draft is superior and the blower in that case simply wastes steam into the atmosphere.
Damper is usually operated by a lever. When closed (pushed down) it chokes the airflow, drastically reducing fire temperature. This is used to reduce steam production when it is no longer needed.