Date: 201201
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Flight conditions: IMC
Light: Daylight
Aircraft: Regional Jet 700 ER/LR (CRJ700)
Operator: Air Carrier
Operating under: Part 121
Flight phase: Descent
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Pneumatic System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Troubleshooting; Confusion
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Aircraft Equipment Problem Critical
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Overcame Equipment Problem; General Declared Emergency
Contributing factors: Human Factors; Aircraft
Primary problem: Aircraft

Narrative: During descent from VMC at FL280 into cloud tops; OAT was such that cowl heat usage was required; and was selected. Cowl heat seemed to operate normally for a short period of time; I would estimate between 1 and 3 minutes. After which the cowl heat caution message posted at a time when the N2 was sufficient for normal operation; followed by an isolation valve caution message; and an abnormally high cabin rate of climb was noticed. Both pilots donned the oxygen mask as it was apparent that the cabin altitude was well beyond its normal range; and increasing rapidly. I then had the First Officer begin the QRH procedure for the isolation valve caution message; and relieved him of all of his other non-flying pilot duties; as per company procedure. I immediately advised ATC that we were having an issue with a valve in the pressurization system and that we needed to continue our descent below our crossing altitude; but we were very close to the crossing intersection; and did have to briefly level as the Controller coordinated descent. Upon stopping descent; cabin altitude began to increase above 8;500 and the CABIN ALT caution message briefly posted; and before I was able to declare an emergency; the Controller had cleared us to 10;000 FT. As we started a high normal rate of descent; the cabin altitude began descending; and through the combination of the descent and the QRH procedure completion; the cabin altitude returned to its normal range during descent. No emergency was declared by the crew; nor was priority requested; but we did advise ATC that we were operating without ice protection and that deviations may be required around clouds; but normal vectors and descent kept us free of icing conditions and we continued to a normal landing.


Second narrative: At about FL230 we got an 'ISOL FAIL' caution message. While performing the QRH; we realized the cabin altitude was climbing. The Captain (pilot flying) contacted ATC and asked for a descent to 10;000 FT. The QRH was completed about the time we reached 10;000 FT and we were able to regain pressurization. The cabin altitude did reach a max of approximately 8;800 FT before we could regain pressurization. ATC declared an emergency for us. We were able to maintain pressurization for the remainder of the descent and landing. The QRH was unclear in what exactly to do for an ISOL FAIL caution message. It should be clarified.


Synopsis: A CRJ-70 flight crew experienced a pneumatic isolation valve failure that led to pressurization issues. The First Officer mentioned the QRH for the problem was 'unclear.'