This is a very complex device .
Essentially device 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 .
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 .