1.   A trained, fit submariner, possibly with breathing apparatus, might do it.

2.   Astronauts have special breathing apparatus.

3.   Four men were forced to use breathing apparatus by the choking smoke.

4.   His own experience would enable him to demonstrate the use of the breathing apparatus, and he volunteered to go down.

5.   It took firemen wearing breathing apparatus nearly two hours to bring the blaze under control.

6.   Shortly after this I nearly suffocated when the pipe of my breathing apparatus came adrift.