OT; A question about vampires and breathing

[JDMeans@xxxxxxx]

Hey gang, I have a question regarding vampires in the Buffyverse.

In past episodes, it has been established that vampires do not breath. Their 
autonomic functions don't work the way that humans do, so they don't breath 
regularly, and have no heartbeats. My question then is; why does Spike carry 
cigarettes? 

Does the fact that Spike likes to light up mean that vampires can inhale at 
will, even though they don't derive oxygen the way we do? And if that's the 
case, why did Angel have Xander perform mouth-to-mouth on Buffy in 'Prophecy 
Girl'? ("You have to breath for her. I have no breath.") Or like a certain 
ex-president, does Spike not inhale?

Just curious, and wanting to stir up some trouble in my little corner of 
Buffy fandom,
Kirayoshi