Something has started burning and it will not wait. You drop whatever you were holding, run towards it, and pour water on it until it stops. Nobody planned this morning around it; it chose the moment, and everything else on the list has to sit and wait until the flames are down.
From the picture
公司裡的救火
同樣的畫面搬進辦公室：沒有真的火，但事情一樣是突然燒起來的，一樣不能等，也一樣把你原本排好的一天整個吃掉。中文的「救火」用法幾乎重疊，所以對台灣讀者特別好記。這是理解上的連結，不是在說哪個用法先出現。
noun · C1
The work of dealing with sudden problems in a company, a machine or a system — finding out what has gone wrong and putting it right at once, instead of getting on with planned work. This use is more common in British English.
救火（處理突發狀況）
noun · B1
The work of stopping fires from burning: reaching the fire, using water, foam or other equipment to put it out, and keeping it from spreading.
滅火（的工作）