On the right-hand side of the engine room, there was a ventilator you could connect to an air purifier. Air purifiers were necessary on submarines, because during long dives, the level of carbon dioxide in the air breathed went up quickly everywhere in the vessel. The bad quality breathing air caused the crew shortness of breath and headaches. 

Vesikko had four engines in total: two diesel engines and two electric engines. The diesel master, diesel NCO and seaman were in charge of the diesel engines. When the submarine was driving, it was very hot in the engine room, and the level of noise was overwhelming. Holding on to a rail with one hand, the men kept lubricating the engines with an oil can in the other. The rocking of the vessel felt stronger at the back and it was difficult to not fall because of the oil made the floor slippery. The engine room floor was often covered with oil, so rubber boots were the best footwear for working there. 

When navigating on the surface, the diesel engines ran the two electric engines, which transmitted power to the propellers for diving. When Vesikko dived, the diesel engines were disconnected from the electric engines, which then started to power the propellers on their own. Vesikko’s 62 batteries were also charged with the diesel engines.