CL65 Captain experiences cabin pressurization anomaly during climb and continues climbing while trouble shooting. A Cabin Altitude Caution at 8000 feet then a Cabin Altitude Warning at 10000 feet; encourages the crew to reverse their climb at 13000 feet. During the descent an altitude deviation occurs. When the problem cannot be corrected the crew elects to return to departure airport.

Narrative

On Departure climb out at an approximate altitude of 7000 ft. Crew began to notice and subsequently discuss that the aircraft cabin altitude seem to climbing at near the same rate of climb as aircraft. As discussion continued cabin climbed to 8000 ft and Crew received the Cabin Altitude caution. Non Flying Pilot (Captain) pulled QRH an attempted to control cabin altitude manually as aircraft continued its climb. Assigned a higher altitude from Center we continued our climb as we worked on the problem. The problem became difficult to handle due to continued distractions i.e. busy airspace; check lists and eventually a call from Flight Attendant that there was a faint haze in the cabin. We eventually determined that it was not smoke but perhaps vapor in the air. As the cabin altitude climbed the Crew received warning (while only momentarily) and rapidly started down from approximately 13000 for 10000 feet. Crew received an intermediate level off at 12000 feet from Center; however our descent rate took us through 12000 feet. We quickly returned to assigned altitude when Center asked about our clearance. We were then assigned 10000 feet. Considering our proximity to the airport; that it was a maintenance base and the fact we had little to no airflow from packs we requested a return to the airport. Once we were established for a return to the airport APU was started to try to improve airflow; Flight Attendant briefed and unpressurized abnormal checklist consulted. Considering time; altitude and workload I resolved to contact Dispatch upon safe return to the airport. The remainder of flight was SOP with an normal approach and landing. I should have been more proactive in managing the situation; i.e. selecting the ALT button at first clue cabin pressure was not normal. Coordinating the change with ATC. Flying the aircraft first then when ready read QRH. Since the event I have a heightened level of awareness of the cabin pressure data.