Ok, nobody jump my a** for these numbers. These are approximations and are state dependent. Some areas of the country still have "volunteer rescue squads". This is meant for areas that have licensed paramedics and EMT's working full/part time for private/hospital based/FD services, etc.
APX Training time & reqs.
1st responder - Shotgun EMT-B class.
EMT Basic - Prereq's: None. 1 semester / 4-6 months class apx. 8 hrs week didactic, apx. 50 hrs. clinical time. Written/practical state/national certification.
EMT Intermediate - Prereq's: EMT-Basic, 1 semsester class apx 8 hrs week didactic, apx 150 hrs. clinical. Written/practical state/national certification.
EMT Paramedic - Prereq's: EMT Intermediate. 2 semesters class apx 12 hrs week didactic, apx. 1000 hrs clinical. Written/practical state/national certification, ACLS (Advanced Cardiac Life Support), PALS (Pediatric Advanced Life Support), AMLS (Advanced Medical Life Support).
EMT Paramedic (Critical Care) - Prereqs: EMT Paramedic. Note: This is an apx. 2 week addendum class that more specifically addresses some issues in critical care transport (incubators, LVAD, Intraaortic balloon pumps, etc.), and if I'm not mistaken is not considered a separate licensing level, though many CC-Pmeds do wear a rocker bar on top of their Paramedic patch.
Some states such as Texas are a little different in that they have their own licensing procedures aside from the National Registry (Think of the medical school application service there).