Baggage is pressurized. Animals ride back there. Baggage is usually
under the floor of the cabin on the big girls and behind the cabin for
the little girls.. The floor is not designed to be strong enough to be
part of the pressure containment vessel.
Michelle

Slip'er wrote:

I just found another fun thing to do on a flight! Thanks. Hmmm...how much
would I freak out a flight attendant when I pull out my laptop with a psia
transducer and start logging data? Is the baggage compartment
unpressurized? I could compare data with a remote logger after the flight
WIFI is frowned upon.



I've monitored the pressure altitude on quite
a few flights on various airlines and have noticed quite a bit of
variation. Some flights were kept very close to the 8000' limit
(around 7900'), while the lowest I've seen while at cruising
altitude was around 5500'.