火箱

Fireboxes are chambers found on steam vehicles , where fuel is burned in order to boil water in boilers . A firebox is positioned such so that it is partly inside a boiler, but also has a cluster of heating tubes extending through the boiler, to a chimney at the other end, where the hot air and smoke pass through.

Coal-powered fireboxes have a firedoor in the vehicle's cab , which can be open to shovel coal inside. The door should be kept closed otherwise, to prevent blowback. Blowback is a dangerous event where exhaust flow is reversed, drawing fire into the cab, potentially catastrophically harming the crew. It happens upon entering tunnels with the firedoor open.

火箱內的溫度能透過一個溫度計監控。火箱應保持在剛好足以產生所需蒸汽量的溫度。溫度過低將無法產生足夠的蒸汽，溫度過高則可能導致燃料消耗效增加。

Firebox temperature is controlled by the amount of coal and airflow inside it. Simply having no more coal to burn will cause the firebox to cool down, and adding more coal will warm it up if the airflow is sufficient. The amount of airflow is key, and depends on whether there is steam being admitted to the cylinders , but can also be adjusted by the blower and damper controls.

Having the firebox full to the brim with coal is not always the best choice. Too much coal with too little airflow negatively affects fuel efficiency , resulting in a lot of coal particles getting spewed out the chimney before fully burning. This is what makes the exhaust dark. When coal amount is proportional to available airflow, however, coal burns cleaner and the exhaust color is more bright.

司機員若要精準控制火箱中的煤炭量，可以選用專家鏟子。使用位於火箱門旁的拉桿也能將火箱內的煤炭自當中排出。.

Coal in fireboxes can be dumped manually, with the coal dump lever found next to the firedoor.