Crew Oxy regulators.
There are different classes of regulators. A to E. Types c,d and e provide pressure breathing. The EMERG setting does not provide pressure breathing despite what a 10 year GIV pilot on this thread claims. The emerge setting is for smoke removal.
EROS mask operating manuals are available from the manufacturers web site and anyone more interested can find TSO-C78, TSO-C89 and TSO-C99 on line too.
Educated yourselves rather than relying on hearsay.