Narrative:

On takeoff roll; the first officer (first officer) and I noticed an 'air whooshing' sound around vr. We both instinctively pushed forward on our window handles; and he said 'that's an odd sound'. With no warning lights; we continued into the air and cleaned up the configuration of the aircraft. The after takeoff checklist showed no abnormalities and the pressurization was working normally. We continued on to fl 350.about 10 minutes prior to top of descent (TOD); at fl 350; first officer and I decided to coordinate a bathroom break with the flight attendants. As first officer was getting ready to leave the flight deck; I pulled out my O2 mask and noticed the secure straps would not inflate and there was no flow sound when I pulled out my mask. It was then that I realized what the 'air whooshing' noise was on takeoff. We checked the flight deck O2 and the gauge read zero. We decided to start a slow descent to fl 250 while we looked up any guidance from the QRH and MEL. We also sent dispatch a message that 'flight deck O2 quantity indicated zero and we were descending to fl 250. Do you know of anything else we should consider?'as we were leveling at FL250; ATC told us to continue to fl 240. Dispatch sent a message telling us there was no guidance or checklist for this situation. Within a couple of minutes; we got cleared to descend and continued our descent to below 10;000 feet to 5;000 feet.during the descent; we notified the flight attendants of our lack of O2 in the flight deck and asked if we could place a portable O2 bottle with two mask in the flight deck to be prepared; in the case we had a rapid depressurization or smoke/fumes. I contacted [personnel in flight operations] and advised him of the incident and asked if he would let me know what maintenance found with the O2. He contacted me with the info that the O2 flight deck bottle had been removed and replaced and the aircraft continued to [the next destination] with the next crew. Some considerations for this incident:there is no checklist for flight deck O2 going to zero in flight (it has always been checked on the ground and if it were zero at that time; we would not go anywhere)if this situation had been noticed earlier in flight; according to the fars; we would have had to descend right away. It was a clear VFR day and we had no alternate fuel. The lower altitude would have a much higher fuel burn; which would have necessitated a divert. This situation could have worse fuel consequences if on [oceanic route] or trans-continental flight.after realizing we had no O2 in the flight deck; we asked the flight attendants to bring us a portable bottle with 2 mask in the event we had a rapid depressurization. With the new full face O2 mask; smoke goggles have been removed. We realized that if a smoke/fumes situation would have developed; the portable O2 bottle with 2 mask would not have been a good situation.

Related reports:

Google
 

Original NASA ASRS Text

Title: B737-900 flight crew reported that while in flight the Crew Oxygen had lost all its pressure. He mentioned he and FO did notice an air wooshing sound on takeoff.

Narrative: On Takeoff roll; the First Officer (FO) and I noticed an 'air whooshing' sound around Vr. We both instinctively pushed forward on our window handles; and he said 'that's an odd sound'. With no warning lights; we continued into the air and cleaned up the configuration of the aircraft. The After Takeoff Checklist showed no abnormalities and the pressurization was working normally. We continued on to FL 350.About 10 minutes prior to Top of Descent (TOD); at FL 350; FO and I decided to coordinate a bathroom break with the flight attendants. As FO was getting ready to leave the flight deck; I pulled out my O2 mask and noticed the secure straps would not inflate and there was no flow sound when I pulled out my mask. It was then that I realized what the 'air whooshing' noise was on takeoff. We checked the flight deck O2 and the gauge read zero. We decided to start a slow descent to FL 250 while we looked up any guidance from the QRH and MEL. We also sent dispatch a message that 'Flight Deck O2 quantity indicated Zero and we were descending to FL 250. Do you know of anything else we should consider?'As we were leveling at FL250; ATC told us to continue to FL 240. Dispatch sent a message telling us there was no guidance or checklist for this situation. Within a couple of minutes; we got cleared to descend and continued our descent to below 10;000 feet to 5;000 feet.During the descent; we notified the flight attendants of our lack of O2 in the flight deck and asked if we could place a Portable O2 bottle with two mask in the flight deck to be prepared; in the case we had a rapid depressurization or smoke/fumes. I contacted [personnel in flight operations] and advised him of the incident and asked if he would let me know what maintenance found with the O2. He contacted me with the info that the O2 flight deck bottle had been removed and replaced and the aircraft continued to [the next destination] with the next crew. Some considerations for this incident:There is NO checklist for flight deck O2 going to zero in flight (it has always been checked on the ground and if it were zero at that time; we would not go anywhere)If this situation had been noticed earlier in flight; according to the FARs; we would have had to descend right away. It was a clear VFR day and we had no alternate fuel. The lower altitude would have a much higher fuel burn; which would have necessitated a divert. This situation could have worse fuel consequences if on [oceanic route] or Trans-continental flight.After realizing we had no O2 in the flight deck; we asked the flight attendants to bring us a portable bottle with 2 mask in the event we had a rapid depressurization. With the new full face O2 mask; smoke goggles have been removed. We realized that if a smoke/fumes situation would have developed; the portable O2 bottle with 2 mask would not have been a good situation.

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.