I have often wondered why the pax masks are different to the ones attached to the crew portable O2 botttles.
Depends on the airline. One I worked for the crew had the medical style clear fitted masks. FD had full face mask. The other (very large B777/A380 operator) crew bottles had the same round yellow masks as pax O2.
Yes it stinks, chemical generator hence the descriptions of 'smelt like fire(burning)'