The Quebec-class was plagued with problems caused by liquid oxygen evaporation. Their endurance was limited to 14 days due to continuous evaporation of the oxygen and lack of a re-liquefaction system, and the propulsion system led to several serious incidents. In 1957 two submarines were lost due to accidents caused by the oxygen system. "M-256" suffered a fire off Tallinn in the Baltic, which led to the loss of 35 men, while "M-351" sank in the Black Sea with no casualties. Other incidents caused oxygen-fueled flames to burst out from the boats, which led to their crews to nickname them "zazhigalka" ("lighters") or Zippos after the well-known cigarette lighter.