Narrative:

The cabin press warning light light came on around FL200 climbing to FL250. As pilot not flying; I checked the cabin altitude and noted that it was at 10;000 ft and climbing at about 300-400 ft/min. We leveled off and requested a descent to 14;000 ft. ATC gave us permission to descend to FL200 and said it would take about 15 seconds to get us lower. As we approached FL200 on a 2;500 ft/min descent; we requested to continue the descent. ATC informed us that it we would have to wait for the descent and we declared an emergency due to slow cabin depressurization. We continued down to 14;000 ft at 2;500 ft/min. During the descent; I contacted the flight attendants and they said other than their ears still popping slightly; there were no other problems. While the first officer flew the airplane; I ran the QRH. At the step where you set the bleeds to maximum; I noticed that the bleed switches were in the off position. I placed the bleed switches back to on and immediately the cabin began to pressurize again. The auto controller stabilized the sudden introduction of bleed air and began to descend the cabin at 500 ft/min. We finished the QRH; and just to be sure that there were no other problems; and that the auto controller was supposed to descend the cabin at 500 ft/min and was not limited to that by a hole or some other discrepancy; I switched to manual control and used the increase/decrease switch to descend the cabin at 1;000 ft/min. The cabin pressurized just fine and once it got below 10;000 ft again; I switched back to auto mode and let the controller take the cabin to the proper altitude. We coordinated with dispatch to let them know what happened; and that the 'problem' was resolved. The cabin returned to its normal altitude; we canceled the emergency; and told ATC that there were no further discrepancies and that the loss of pressurization was due to a switch being bumped. We climbed back up to 17;000 ft and continued the flight to destination.the takeoff was conducted with the bleeds on; and during the climb checklist; the differential was increasing; and the cabin was not climbing. I definitely checked the pressurization during the climb checklist. When the cabin pressurization light illuminated; we had between 4.0 and 5.0 psi differential and it was slowly dropping. I believe; after analyzing the situation; that while I was adjusting the cabin temperature I either bumped the bleed switches to the off position by accident; or at some point I may have inadvertently placed the bleed switches to the off position during a flow. My best guess as to what happened is that after checking the pressurization gauges and cabin temperature during the climb checklist; I may have flicked the bleed switches to off. I don't remember placing the switches in the off position; and I wouldn't ever have any reason to do so under normal conditions. I don't think I actually switched the switches at that time; but I also can't think of any other time other than adjusting the cabin temperature that I reached up to that panel. Contributing to this error was the fact that this was the fifth leg on an 11 hour day and it was dark. I did not feel fatigued or tired; and I got plenty of sleep the night before. My normal sleep schedule has me well awake during the time when this flight was scheduled. Being dark may have made switch confusion more likely; but I don't have any reason to reach all the way over to the other side of the panel to turn off anything during the climb.

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Original NASA ASRS Text

Title: Q400 Captain experienced a cabin pressure warning light climbing through FL200. An emergency was declared and descent initiated. During the QRH procedure the engine bleeds were discovered off and placed on; solving the problem.

Narrative: The CABIN PRESS warning light light came on around FL200 climbing to FL250. As pilot not flying; I checked the cabin altitude and noted that it was at 10;000 FT and climbing at about 300-400 FT/MIN. We leveled off and requested a descent to 14;000 FT. ATC gave us permission to descend to FL200 and said it would take about 15 seconds to get us lower. As we approached FL200 on a 2;500 FT/MIN descent; we requested to continue the descent. ATC informed us that it we would have to wait for the descent and we declared an emergency due to slow cabin depressurization. We continued down to 14;000 FT at 2;500 FT/MIN. During the descent; I contacted the Flight Attendants and they said other than their ears still popping slightly; there were no other problems. While the First Officer flew the airplane; I ran the QRH. At the step where you set the bleeds to MAX; I noticed that the bleed switches were in the OFF position. I placed the bleed switches back to ON and immediately the cabin began to pressurize again. The auto controller stabilized the sudden introduction of bleed air and began to descend the cabin at 500 FT/MIN. We finished the QRH; and just to be sure that there were no other problems; and that the auto controller was supposed to descend the cabin at 500 FT/MIN and was not limited to that by a hole or some other discrepancy; I switched to manual control and used the increase/decrease switch to descend the cabin at 1;000 FT/MIN. The cabin pressurized just fine and once it got below 10;000 FT again; I switched back to auto mode and let the controller take the cabin to the proper altitude. We coordinated with Dispatch to let them know what happened; and that the 'problem' was resolved. The cabin returned to its normal altitude; we canceled the emergency; and told ATC that there were no further discrepancies and that the loss of pressurization was due to a switch being bumped. We climbed back up to 17;000 FT and continued the flight to destination.The takeoff was conducted with the bleeds on; and during the climb checklist; the differential was increasing; and the cabin was not climbing. I definitely checked the pressurization during the climb checklist. When the cabin pressurization light illuminated; we had between 4.0 and 5.0 PSI differential and it was slowly dropping. I believe; after analyzing the situation; that while I was adjusting the cabin temperature I either bumped the bleed switches to the off position by accident; or at some point I may have inadvertently placed the bleed switches to the OFF position during a flow. My best guess as to what happened is that after checking the pressurization gauges and cabin temperature during the climb checklist; I may have flicked the bleed switches to off. I don't remember placing the switches in the OFF position; and I wouldn't ever have any reason to do so under normal conditions. I don't think I actually switched the switches at that time; but I also can't think of any other time other than adjusting the cabin temperature that I reached up to that panel. Contributing to this error was the fact that this was the fifth leg on an 11 hour day and it was dark. I did not feel fatigued or tired; and I got plenty of sleep the night before. My normal sleep schedule has me well awake during the time when this flight was scheduled. Being dark may have made switch confusion more likely; but I don't have any reason to reach all the way over to the other side of the panel to turn off anything during the climb.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.