Narrative:

We were flying our third leg of the day. We had multiple MEL's on the aircraft one of which was deferred left pack that we deferred. We pushed and then had a gate return for an associated maintenance item that had to be addressed that popped up after we left the gate. After a quick visit from maintenance personnel we pushed. We took off without any issues. During climb out around 18;000 feet our right pack (the only operational pack on the aircraft) did an uncommanded shutdown. We had no EICAS cautions or warnings when the pack shut down we simply got an right pack off status message. The cabin was now not being pressurized and the cabin altitude was rising. I called for our immediate action items for a cabin altitude/ emergency descent. At that point we [notified ATC] and performed our emergency descent. No passenger oxygen masks deployed during this event. We ran all check lists and got all pertinent airport data for [diversion airport] and landed without issue. I detected the malfunction in flight prior to any of the cabin altitude cautions or warnings. The left pack had shut down by itself during our taxi in to the gate. We attempted to trouble shoot the problem with maintenance to no avail and we deferred the left pack. We pushed off the gate for our flight back and during taxi out after we started the left engine we got an intermittent left pack hi temperature caution message. We called maintenance who advised us to return to the gate. We did that and maintenance came out and performed the required work and signed the aircraft off. We deplaned the passengers and had ground air conditioning hooked up to the aircraft due to the high cabin temperature. We then pushed back and departed without any issues. During climb out we were being pressurized off the right engine bleed and had a successful swap of bleed air from the APU. While climbing up to 25;000 feet around 18;000 feet we encountered icing conditions and turned on the cowl anti-ice system. I checked the ecs (environmental control system) page after we turned it on and had no issues. Shortly after that I felt a sudden stop of air from the cooling vents in the flight deck. I immediately looked at EICAS and saw an right pack off status message. I went to the ecs page and our right pack was colored white and off. I immediately tried to cycle the pack. It did not restart. We at no time got an over pressure or over temperature caution/warning on EICAS. We were now not being pressurized and the cabin altitude was increasing. We did our immediate action items for a cabin altitude/emergency descent; declared and emergency and executed our descent to 8;000 feet. The first officer called the flight attendant to give him the [checklist] items. We finished all of our checklists at 8;000 feet while being vectored by ATC. We got ATIS; performance data and briefings done and were vectored for the approach and landed without issue and taxied to our gate where we deplaned. I cycled the pack and that did not work. I commanded the cabin altitude/emergency descent immediate action items and the associated checklist. We began our emergency descent to an ATC assigned altitude of 8;000 feet. The cabin altitude reached 10;000 feet as we descended thru 10;000 feet. We finished our checklists once we leveled off at 8;000 feet. We went O2 masks off and finished the non immediate action items portion of the check list. We got landing data; ATIS; and pertinent information for an ILS and landed without issue. Don't allow single pack 200's to operate revenue flights.

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Original NASA ASRS Text

Title: Air carrier Flight Crew reported loss of pressurization and diverting for an emergency landing.

Narrative: We were flying our third leg of the day. We had multiple MEL's on the aircraft one of which was deferred left pack that we deferred. We pushed and then had a gate return for an associated maintenance item that had to be addressed that popped up after we left the gate. After a quick visit from maintenance personnel we pushed. We took off without any issues. During climb out around 18;000 feet our right pack (the only operational pack on the aircraft) did an uncommanded shutdown. We had no EICAS cautions or warnings when the pack shut down we simply got an R Pack Off status message. The cabin was now not being pressurized and the cabin altitude was rising. I called for our immediate action items for a CABIN ALT/ EMER DESCENT. At that point we [notified ATC] and performed our emergency descent. No passenger oxygen masks deployed during this event. We ran all check lists and got all pertinent airport data for [diversion airport] and landed without issue. I detected the malfunction in flight prior to any of the cabin altitude cautions or warnings. The left pack had shut down by itself during our taxi in to the gate. We attempted to trouble shoot the problem with Maintenance to no avail and we deferred the left pack. We pushed off the gate for our flight back and during taxi out after we started the left engine we got an intermittent left pack HI TEMP caution message. We called Maintenance who advised us to return to the gate. We did that and Maintenance came out and performed the required work and signed the aircraft off. We deplaned the passengers and had ground air conditioning hooked up to the aircraft due to the high cabin temperature. We then pushed back and departed without any issues. During climb out we were being pressurized off the right engine bleed and had a successful swap of bleed air from the APU. While climbing up to 25;000 feet around 18;000 feet we encountered icing conditions and turned on the cowl anti-ice system. I checked the ECS (Environmental Control System) page after we turned it on and had no issues. Shortly after that I felt a sudden stop of air from the cooling vents in the flight deck. I immediately looked at EICAS and saw an R Pack Off Status message. I went to the ECS page and our right pack was colored white and off. I immediately tried to cycle the pack. It did not restart. We at no time got an over pressure or over temperature caution/warning on EICAS. We were now not being pressurized and the cabin altitude was increasing. We did our immediate action items for a CABIN ALT/EMER DESCENT; declared and emergency and executed our descent to 8;000 feet. The First Officer called the flight attendant to give him the [checklist] items. We finished all of our checklists at 8;000 feet while being vectored by ATC. We got ATIS; performance data and briefings done and were vectored for the approach and landed without issue and taxied to our gate where we deplaned. I cycled the PACK and that did not work. I commanded the CABIN ALT/EMER DESCENT immediate action items and the associated checklist. We began our emergency descent to an ATC assigned altitude of 8;000 feet. The cabin altitude reached 10;000 feet as we descended thru 10;000 feet. We finished our checklists once we leveled off at 8;000 feet. We went O2 Masks off and finished the non immediate action items portion of the check list. We got landing data; ATIS; and pertinent information for an ILS and landed without issue. Don't allow single PACK 200's to operate revenue flights.

Data retrieved from NASA's ASRS site 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.