O. Sami Saydjari wrote:
OK, very helpful answers. But, how does one get a "pressurized mask"?

Here's a low pressure model.
http://www.mhoxygen.com/index.phtml?...product_id=373

Here's this retailer's entire offering.
http://www.mhoxygen.com/index.phtml?...prd_group_id=9

George Patterson
"Naked" means you ain't got no clothes on; "nekkid" means you ain't got
no clothes on - and are up to somethin'.