Firefighter has a container in which you can store fuel, it will automatically add fuel from the container when its fuel level drops to 0%.
Note: Left click on the firefighter will open its container. However, DO NOT left click on the firefighter while you are holding fuel under the mouse pointer, that will directly add fuel to the firefighter instead of putting fuel into its container.
And if you also subscribed the mod "Ice Fling Range Check", you need to press ALT when click on the firefighter to fore inspect.

给灭火器增加一个储物栏，里面可以放燃料，当燃料值降低到0%时，灭火器会自动从储物栏添加燃料。
注意：在灭火器上单击鼠标左键可以打开储物栏，注意不要在鼠标拿着燃料的时候左键点击灭火器，这样会直接给灭火器加燃料，而不是放到储物栏里。
如果你还订阅了“灭火器范围显示”的mod，需要在左键点击灭火器的时候按住ALT键才能正确显示灭火器范围。