Regional Jet 700 ER/LR (CRJ700)
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Less Severe
Flight Crew Returned To Departure Airport; General Maintenance Action
Aircraft
Prior to our flight I reviewed and completed the MEL procedure for a deferral regarding the automatic pressurization system. The system test was successful. However; we received a CABIN ALT caution message climbing through FL180. We leveled out at FL190 and began to don oxygen masks when a CABIN ALT warning message appeared. The cabin altitude read 10;900 by the time we [notified ATC of urgent situation] with Center and began an [urgent] descent to 10;000 feet. The FO was the flying pilot and I completed the Immediate Action Items and QRH. We landed safely without further incident. There were three non-revenue passengers onboard but no one was hurt and the cabin oxygen masks did not deploy nor were required. Another crew had written up a similar incident the day before.The threat was a loss of cabin pressurization; which may have been caused by a faulty pressure controller. After maintenance was notified on the ground they conducted an ops check and said it was good. The cause of the malfunction was not fully determined.We acted according to procedures but in the future when dealing with an aircraft that has had issues with the pressurization system; I will pay greater attention to the cabin pressure in order to detect a possible malfunction earlier and possibly before receiving an EICAS message; thereby giving us a head start and more time to react.
CRJ-700 Captain reported loss of cabin pressure climbing through FL180. ATC was notified of the urgent situation and the flight returned to departure airport.