B737-800 first officer reported a loss of pressurization at altitude and resulting emergency descent...

Narrative:

Delayed departure due to aircraft being towed over from a maintenance hangar. Departure from runway 26L at ZZZ and flew SID with approved deviations to avoid buildups to the northwest. At approximately [time] EDT; just after leveling off at 33K' and nne of zzzzz; cabin altitude warning light came on with audible horn and cabin altitude climbing through 10K'. We donned oxygen masks; established communications; and captain pulled out the qrc to run the cabin altitude warning checklist. As the cabin altitude continued to rise past towards 12K'; we [notified] ATC (ZZZ center) and initiated a descent to 10K' and continued with qrc procedures. During descent we turned west toward the shoreline; asked for current/forecast weather conditions and decided to divert to ZZZ1. Captain continued to run the emergency checklist referencing the QRH from the ipad. After cabin altitude was indicating below 10K' we took oxygen masks off. After approximately 5-10 minutes with the masks off; I felt some 'hypoxia like' symptoms and told the captain I needed to go back on the oxygen. We both donned the masks again until descending through 6K' at which point the symptoms previously experienced had gone away. Captain was in communications with the cabin throughout the event and we both acknowledged and sent messages to the company via ACARS. Both the approach and landing on runway 17L at ZZZ1 were uneventful and as briefed.

Original NASA ASRS Text

Title: B737-800 First Officer reported a loss of pressurization at altitude and resulting emergency descent. Pilot reported possible hypoxia.

Narrative: Delayed departure due to aircraft being towed over from a maintenance hangar. Departure from RWY 26L at ZZZ and flew SID with approved deviations to avoid buildups to the Northwest. At approximately [time] EDT; just after leveling off at 33K' and NNE of ZZZZZ; CABIN ALTITUDE warning light came on with audible horn and cabin altitude climbing through 10K'. We donned oxygen masks; established communications; and Captain pulled out the QRC to run the Cabin Altitude Warning checklist. As the cabin altitude continued to rise past towards 12K'; we [notified] ATC (ZZZ Center) and initiated a descent to 10K' and continued with QRC procedures. During descent we turned west toward the shoreline; asked for current/forecast weather conditions and decided to divert to ZZZ1. Captain continued to run the emergency checklist referencing the QRH from the iPad. After cabin altitude was indicating below 10K' we took oxygen masks off. After approximately 5-10 minutes with the masks off; I felt some 'hypoxia like' symptoms and told the Captain I needed to go back on the oxygen. We both donned the masks again until descending through 6K' at which point the symptoms previously experienced had gone away. Captain was in communications with the cabin throughout the event and we both acknowledged and sent messages to the company via ACARS. Both the approach and landing on RWY 17L at ZZZ1 were uneventful and as briefed.

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.

Attributes
ACN	1643506
Time
Date	201905
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	B737-800
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Pressurization System
Person 1
Function	Pilot Flying First Officer
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine
Experience	Flight Crew Total 3400
Events
Anomaly	Aircraft Equipment Problem Critical Flight Deck / Cabin / Aircraft Event Illness

B737-800 first officer reported a loss of pressurization at altitude and resulting emergency descent. Pilot reported possible hypoxia.