The third phase of testing for submarine fitness is escape training, utilizing the "Steinke hood submarine escape appliance", or colloquially known as the Steinke hood or, more familiarly, as "Stinky hood". This is a very complex device, but essentially it covers the head and shoulders during ascent from a stranded submarine, allowing air to escape during ascent, which is necessary as the expanding air in the lungs would otherwise cause disastrous injury. Actual training with the Steinke Hood is done in a Submarine Escape Training Tower to simulate a submarine stranded on the floor of the sea bed.