Narrative:

Climbing out and approaching FL240 we received a master warning for left bleed duct. The autopilot was on. The pilot flying took the radios and had the flight controls as I ran the QRH checklist. The checklist states that all bleed air sources could be closed after 30 seconds; causing loss of pressurization if the warning persists for 30 seconds. A timer was started by the PF at this point. It also notes that the warning message would be replaced by a caution message stating left bleed duct following automatic bleed closure and bleed isolation. I then ran the portion of the checklist which states 'if either left or right bleed valves are open:' since at this point the ecs [environmental control synoptic) page for the left side showed the left side duct work all red; and green on the right with the isolation valve closed and right bleed open. With the checklist completed thirty seconds had passed; the left bleed caution had appeared as expected; and pressurization was normal off the right engine bleed. The checklist made no statement about monitoring cabin pressure; landing at the nearest suitable airport etc.; only about leaving icing conditions. Having done this I turned my attention to whether to continue the flight to destination; or to return to the departure airport. Weather was suitable at both airports. I then started the APU with the possibility of selecting that as a bleed source. I SELCAL'ed dispatch. While dispatch checked with maintenance and calculated a possible fuel burn for continuing I rechecked the bleed configuration on the ecs page and noted that the right engine bleed had closed. (There was no cabin altitude caution or warning message.) the need to descend immediately was obvious. PF requested a descent to 10;000 feet and was immediately given it. (An emergency was not declared since the request was immediately granted.) as we were descending dispatch tried to call us back and then ZZZ radio tried to contact us. Because we were descending they were unable to hear our response. As we descended ATC asked if we needed to declare an emergency. As PIC I answered this rather than the PF; saying that we did not need to declare an emergency at that time. I was prepared to declare an emergency if need be; but we were cleared to 10;000 feet which was the only assistance we would have immediately needed. In the descent I tried to select the APU as a bleed source; and reselected the right engine. This was not checklist directed and proved unsuccessful. As we descended rapidly I advised the flight attendants and the passengers. I explained the lack of bleed source and that that was reason for the heat building in the cabin. Also I advised them that we would be landing in 20 minutes or so. Shortly thereafter we received a cabin altitude caution message and then a cabin altitude warning message at about 16000. I ran the QRH procedure for the cabin altitude warning; which commanded pass oxy switch on. I did this and then later followed up with another call to flight attendant one to verify if the masks had dropped and were being used and a very brief PA about why the masks had dropped. The unpressurized flight procedure (packs on) was called for if cabin pressurization could not be controlled. The left pack was selected off per the earlier checklist and the right pack was not on in the sense that it had no bleed supply so the checklist was not run. With the very high workload of the descent I had intentionally skipped over the portion of the original checklist for 'if left and right bleed valves are closed' since at the time I ran the checklist they were not both closed. Prioritizing; we descended first and did not actually have the left bleed duct master warning anymore. This checklist also calls for the unpressurized flight procedure (packs off) which I did run. All the events described so far took perhaps six minutes before level off at a safe altitude. We were established in the descent with four minutes on the PF's clock. As we leveled off at 10;000 feet the flight became much more normal. The PF and I agreed that there was no real reason for an emergency to be declared at this point. We removed our oxygen masks. The checklists were carefully reviewed. The need for a gradual descent was expressed to ATC for passenger comfort. An unpressurized approach and landing was accomplished without incident. There were no injuries; although I understood later that one passenger was feeling ill.with the left bleed caution message I visually confirmed that the left bleed had closed; which it had; and that the right bleed was still open; which it was. Completing the checklist took 30 seconds; and once the checklist had been completed I assumed that it would stay open. This was an incorrect assumption and led me to consider continuing to destination when a descent was soon called for. A situation in which all bleed sources are lost should have no such ambiguity on the EICAS and we should not have to wait for a cabin altitude warning to see the issue. The checklist should reinforce the possibility of bleed closure at the end; and a descent could have been initiated much sooner. Restating. The checklist was complete; and now with a high workload I started looking at the FMS; using SELCAL; etc. The realization that we were de-pressurizing was masked by these other tasks until I scanned the ecs page again. The checklist must make it crystal clear that the aircraft could still potentially be without any bleed source; as happened to us; instead of simply saying 'could'. And continuing to monitor cabin pressure is the fix here. That is how we caught it; because the other signs are subtle. There was no popping of ears; only a slow warming which you get single pack anyway. Again I think landing at the nearest suitable airport should follow. The cabin altitude warning checklist actually only recommends immediate descent; but does not proscribe a rapid descent. Immediate rapid descent would be a better phrase here. It is how I was trained and how it was flown; but the checklist doesn't specify any descent rate and I think it should. While not really an issue in our flight; other than a small distraction; there could be some misunderstanding of the meaning of packs on in the cabin alt checklist. This could perhaps be interpreted to either mean if packs are only selected on; or selected on and operating. Additionally; I would have declared an emergency if I had to do it over since a potentially more hazardous situation could have occurred if the descent had not been initiated when it was.

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Original NASA ASRS Text

Title: A CRJ-900 suffered a loss of pressurization when the Flight Crew attempted to deal with a L BLEED DUCT EICAS warning.

Narrative: Climbing out and approaching FL240 we received a master warning for L BLEED DUCT. The autopilot was on. The pilot flying took the radios and had the flight controls as I ran the QRH checklist. The checklist states that all bleed air sources could be closed after 30 seconds; causing loss of pressurization if the warning persists for 30 seconds. A timer was started by the PF at this point. It also notes that the warning message would be replaced by a caution message stating L BLEED DUCT following automatic bleed closure and bleed isolation. I then ran the portion of the checklist which states 'If either L or R bleed valves are open:' since at this point the ECS [Environmental Control Synoptic) page for the left side showed the left side duct work all red; and green on the right with the isolation valve closed and right bleed open. With the checklist completed thirty seconds had passed; the LEFT BLEED caution had appeared as expected; and pressurization was normal off the right engine bleed. The checklist made no statement about monitoring cabin pressure; landing at the nearest suitable airport etc.; only about leaving icing conditions. Having done this I turned my attention to whether to continue the flight to destination; or to return to the departure airport. Weather was suitable at both airports. I then started the APU with the possibility of selecting that as a bleed source. I SELCAL'ed Dispatch. While Dispatch checked with Maintenance and calculated a possible fuel burn for continuing I rechecked the bleed configuration on the ECS page and noted that the right engine bleed had closed. (There was no CABIN ALT caution or warning message.) The need to descend immediately was obvious. PF requested a descent to 10;000 feet and was immediately given it. (An emergency was not declared since the request was immediately granted.) As we were descending Dispatch tried to call us back and then ZZZ radio tried to contact us. Because we were descending they were unable to hear our response. As we descended ATC asked if we needed to declare an emergency. As PIC I answered this rather than the PF; saying that we did not need to declare an emergency at that time. I was prepared to declare an emergency if need be; but we were cleared to 10;000 feet which was the only assistance we would have immediately needed. In the descent I tried to select the APU as a bleed source; and reselected the right engine. This was not checklist directed and proved unsuccessful. As we descended rapidly I advised the flight attendants and the passengers. I explained the lack of bleed source and that that was reason for the heat building in the cabin. Also I advised them that we would be landing in 20 minutes or so. Shortly thereafter we received a CABIN ALT caution message and then a CABIN ALT warning message at about 16000. I ran the QRH procedure for the CABIN ALT warning; which commanded PASS OXY switch ON. I did this and then later followed up with another call to FA one to verify if the masks had dropped and were being used and a very brief PA about why the masks had dropped. The Unpressurized Flight Procedure (packs on) was called for if cabin pressurization could not be controlled. The left pack was selected off per the earlier checklist and the right pack was not on in the sense that it had no bleed supply so the checklist was not run. With the very high workload of the descent I had intentionally skipped over the portion of the original checklist for 'If left and right bleed valves are closed' since at the time I ran the checklist they were not both closed. Prioritizing; we descended first and did not actually have the L BLEED DUCT master warning anymore. This checklist also calls for the Unpressurized Flight Procedure (packs off) which I did run. All the events described so far took perhaps six minutes before level off at a safe altitude. We were established in the descent with four minutes on the PF's clock. As we leveled off at 10;000 feet the flight became much more normal. The PF and I agreed that there was no real reason for an emergency to be declared at this point. We removed our oxygen masks. The checklists were carefully reviewed. The need for a gradual descent was expressed to ATC for passenger comfort. An unpressurized approach and landing was accomplished without incident. There were no injuries; although I understood later that one passenger was feeling ill.With the L BLEED caution message I visually confirmed that the left bleed had closed; which it had; and that the right bleed was still open; which it was. Completing the checklist took 30 seconds; and once the checklist had been completed I assumed that it would stay open. This was an incorrect assumption and led me to consider continuing to destination when a descent was soon called for. A situation in which all bleed sources are lost should have no such ambiguity on the EICAS and we should not have to wait for a CABIN ALT warning to see the issue. The checklist should reinforce the possibility of bleed closure at the end; and a descent could have been initiated much sooner. Restating. The checklist was complete; and now with a high workload I started looking at the FMS; using SELCAL; etc. The realization that we were De-pressurizing was masked by these other tasks until I scanned the ECS page again. The checklist must make it crystal clear that the aircraft could still potentially be without any bleed source; as happened to us; instead of simply saying 'could'. And continuing to monitor cabin pressure is the fix here. That is how we caught it; because the other signs are subtle. There was no popping of ears; only a slow warming which you get single pack anyway. Again I think landing at the nearest suitable airport should follow. The CABIN ALT warning checklist actually only recommends immediate descent; but does not proscribe a rapid descent. Immediate rapid descent would be a better phrase here. It is how I was trained and how it was flown; but the checklist doesn't specify any descent rate and I think it should. While not really an issue in our flight; other than a small distraction; there could be some misunderstanding of the meaning of packs on in the Cabin Alt checklist. This could perhaps be interpreted to either mean if packs are only selected on; or selected on and operating. Additionally; I would have declared an emergency if I had to do it over since a potentially more hazardous situation could have occurred if the descent had not been initiated when it was.

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.