Narrative:

Bleed configuration checklist monitor crosscheck. Preflight and setup normal. 4th flight flying together as a crew. Effective crew working well together. [It was a] heavy aircraft on asphalt so [we] decided to do [a] 2 engine taxi. Pushed back; started engines; and taxied to runway. While taxiing out; [the] cockpit seemed unusually warm and we adjusted control [for the] cabin as well as [the] passenger cabin temperature controls; trying to cool the entire aircraft. Chalking it up to typical 737 temperature control nuances; we took [to] the runway and departed in anticipation that the system would settle down to normal temperature control once airborne.takeoff and climb seemed uneventful until approaching 10;000 ft. The cabin was still quite warm and we both looked up at overhead panel then we both realized nearly simultaneously that we were not properly configured or pressurized. The proper bleed/pack configuration was then immediately achieved while I arrested our ascent to keep cabin altitude below 10;000 ft. Upon confirmation of configuration and pressurization; we continued the climb for [the] remainder of the uneventful flight.initial cause: incomplete/improper configuration of bleed panel after start. First unrecognized sign of potential problem was unusually warm cockpit and cabin temperatures. That was our first chance to catch our mistake but we missed it; looking at only temperatures; not airflow/duct pressure. On before takeoff checklist: first officer (first officer) stated 'air conditioning and pressurization; set.' I; captain; did not look up to verify. I was taxiing. On after takeoff checklist: first officer/pm (pilot monitoring) stated 'engine bleeds and packs; on and auto.' I; captain; did not look up to verify. I was hand flying. After takeoff; confirmation of initial pressurization was not achieved. 10;000 ft. Check is where we saw and rectified the problem.proper bleed configuration and cabin pressurization [was] achieved prior to cabin altitude reaching 10;000 ft. So no emergency/immediate actions were required. Upon extensive debrief enroute; and not trying to come up with excuses but to truly pinpoint what had really happened; other contributing factors were also identified. First officer states that in his prior aircraft; the overhead panel used a different logic than the 737. In his prior aircraft; up is on and down is off; whereas on the 737; forward is on and back is off. It's subtle; but muscle memory very well could play a factor in this. Also; we were both wearing noise canceling headphones and communicating on [the] interphone. Cockpit noise; or the lack thereof; could have contributed to our lack of awareness that the bleed system was improperly configured due to the lack [of] normal pneumatic noises that was not recognized.upon further recollection; when we arrived at the aircraft; boarding was already underway. After greeting flight attendants [and] stowing my bags; I began to settle in and begin cockpit setup. I do recall that that during the setup; the window heat was off so I turned it on. I don't specifically remember the bleed configuration but would like to think that if it was incorrect; I would have caught and repaired it. Nothing of note stood out at that point. As I was finishing with the overhead panel; I then noticed that the APU was left running by the previous crew. Aircraft electrical power was being supplied by ground power and the packs were off. Ground air was not connected to the aircraft. Since at this point it was about 30 minutes to scheduled departure; I transferred electric power to the APU. I then turned on the packs to supply conditioned air for the cabin. In doing so; at that time; it is entirely possible that I misconfigured the engine bleed air switches but do not specifically recall manipulating them one way or the other. The fact that window heat was off and APU was left running but not supplying power leads to another possibility that the engine bleed air switches werealso left in the wrong configuration by the previous crew and it went unnoticed. Either way; if that was the case; it should have been caught and corrected on [the] captain's initial setup. End result; the error of commission was that the engine bleed air switches were configured wrong. We still cannot identify when the error occurred. The error(s) of omission is that we missed at least 4 opportunities to correct the mistake before eventually discovering it.

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Original NASA ASRS Text

Title: B737 Captain reported improperly configuring pressurization system prior to takeoff.

Narrative: Bleed configuration checklist monitor crosscheck. Preflight and setup normal. 4th flight flying together as a crew. Effective crew working well together. [It was a] heavy aircraft on asphalt so [we] decided to do [a] 2 engine taxi. Pushed back; started engines; and taxied to runway. While taxiing out; [the] cockpit seemed unusually warm and we adjusted control [for the] cabin as well as [the] passenger cabin temperature controls; trying to cool the entire aircraft. Chalking it up to typical 737 temperature control nuances; we took [to] the runway and departed in anticipation that the system would settle down to normal temperature control once airborne.Takeoff and climb seemed uneventful until approaching 10;000 ft. The cabin was still quite warm and we both looked up at overhead panel then we both realized nearly simultaneously that we were not properly configured or pressurized. The proper bleed/pack configuration was then immediately achieved while I arrested our ascent to keep cabin altitude below 10;000 ft. Upon confirmation of configuration and pressurization; we continued the climb for [the] remainder of the uneventful flight.Initial cause: Incomplete/improper configuration of bleed panel after start. First unrecognized sign of potential problem was unusually warm cockpit and cabin temperatures. That was our first chance to catch our mistake but we missed it; looking at only temperatures; not airflow/duct pressure. On Before Takeoff Checklist: FO (First Officer) stated 'Air conditioning and pressurization; SET.' I; Captain; did not look up to verify. I was taxiing. On After Takeoff Checklist: FO/PM (Pilot Monitoring) stated 'Engine bleeds and packs; On and Auto.' I; Captain; did not look up to verify. I was hand flying. After takeoff; confirmation of initial pressurization was not achieved. 10;000 ft. check is where we saw and rectified the problem.Proper bleed configuration and cabin pressurization [was] achieved prior to cabin altitude reaching 10;000 ft. so no emergency/immediate actions were required. Upon extensive debrief enroute; and not trying to come up with excuses but to truly pinpoint what had really happened; other contributing factors were also identified. FO states that in his prior aircraft; the overhead panel used a different logic than the 737. In his prior aircraft; UP is on and DOWN is off; whereas on the 737; FORWARD is on and BACK is off. It's subtle; but muscle memory very well could play a factor in this. Also; we were both wearing noise canceling headphones and communicating on [the] interphone. Cockpit noise; or the lack thereof; could have contributed to our lack of awareness that the bleed system was improperly configured due to the lack [of] normal pneumatic noises that was not recognized.Upon further recollection; when we arrived at the aircraft; boarding was already underway. After greeting flight attendants [and] stowing my bags; I began to settle in and begin cockpit setup. I do recall that that during the setup; the window heat was off so I turned it on. I don't specifically remember the bleed configuration but would like to think that if it was incorrect; I would have caught and repaired it. Nothing of note stood out at that point. As I was finishing with the overhead panel; I then noticed that the APU was left running by the previous crew. Aircraft electrical power was being supplied by ground power and the packs were off. Ground air was not connected to the aircraft. Since at this point it was about 30 minutes to scheduled departure; I transferred electric power to the APU. I then turned on the packs to supply conditioned air for the cabin. In doing so; at that time; it is entirely possible that I misconfigured the engine bleed air switches but do not specifically recall manipulating them one way or the other. The fact that window heat was off and APU was left running but not supplying power leads to another possibility that the engine bleed air switches werealso left in the wrong configuration by the previous crew and it went unnoticed. Either way; if that was the case; it should have been caught and corrected on [the] Captain's initial setup. End result; the error of commission was that the engine bleed air switches were configured wrong. We still cannot identify when the error occurred. The error(s) of omission is that we missed at least 4 opportunities to correct the mistake before eventually discovering it.

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.