Сифон и поддувало

Интенсивность горения топлива, а, как следствие, и температура топки, регулируются подачей воздуха в топку. Кислород воздуха усиливает огонь.

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.

Вдобавок, есть ещё два элемента управления, предназначенные для регулирования тяги: сифон и поддувало.

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.

See also: Regulator, Firebox