Finally, calm

 is a Sunless Sea Random Event. It's basically the same event as A sudden calm.

Trigger conditions
 is triggered at zee if you have 10000 Engine Power or more for a period of time after the  Fire! event and if you have  The Serpentine equipped to your ship. Technically it's not a Random Event since it will come up pretty quickly afterwards.

Event description
The smoke pouring from the deck hatch ceases. Your Chief Engineer emerges.