  In this paper, we obtain new drift-type conditions for nonexplosion and
explosion for nonhomogeneous Markov pure jump processes in Borel state spaces.
The conditions are sharp; e.g., the one for nonexplosion is necessary if the
state space is in addition locally compact and the $Q$-function satisfies weak
Feller-type and local boundedness conditions. We comment on the relations of
our conditions with the existing ones in the literature, and demonstrate some
possible applications.
