(UTC) 

 :It might be intended to mean 30 seconds.  
 :There is a lot about this section that appears ambiguous, and is very poorly referenced for material that is quite different from conventional practice and standard diving physiology texts. Exceptional claims require reliable evidence, and this is entirely absent. If anyone knows of references, please either cite them in the article or mention them here. • • •   05:50, 26 September 2014