Four workers die in Bangkok sewer

Its  called apnoea lack of oxygen. There is oxygen but not enough to sustain life, This type of accident happens  a lot, It happened in England too, four guys died, They was working in a deep drain , the first dropped down then two others did the same trying to rescue him,, then another tried and the same happened to him , The fifth had enough sense not to go down to them but phoned for the rescue services , (fire brigade), So its not just Thaland.