Narrative:

At cruise when the first officer went to the lav; I pulled out my oxygen mask to put on; and the inflatable harness would not fully inflate. I could barely get the mask down over my face; with the size the mask was inflated. The three companies that inspect/overhaul the oxygen masks need to ensure the harness inflates to the specific size required by the manufacture and size the FAA certified it at. When I wrote this same issue up a few years back; [company] disregarded my input and informed me that maintenance inspects the mask a minimum of every six days. Unfortunately; maintenance only removes the mask; and ensures the mask inflates within two seconds. Maintenance does not ensure that mask inflates to a specific size; or even fits over their head. I believe that maintenance should inspect the two-piece oxygen masks to ensure that the harnesses inflate to the specific certified size. The three overhaul companies at the time did not verify the oxygen harness inflated to a set size. I am not sure if they do this today. If not; I question why this is not being done. If recent training is any indication; pilots are more likely to have a depressurization event than a V1 cut. I would request the specified distance from the soft rubber on the mask to the back of the harness; so I can know exactly if I should have the mask replaced. I would rather not be 'that pilot' that writes things up that do not need to be fixed. Since my first write up; I remove my mask every flight in non-compliance with the aom; but was told I was allowed per the check-airmen I have asked. I have written up the harnesses numerous times to have them replaced. I am writing this [report]; as this is the second mask I had to replace in my last two pairings.

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Original NASA ASRS Text

Title: B737-700 Captain reported the quick-donning oxygen mask harness did not fully inflate during cruise.

Narrative: At cruise when the First Officer went to the lav; I pulled out my oxygen mask to put on; and the inflatable harness would not fully inflate. I could barely get the mask down over my face; with the size the mask was inflated. The three companies that inspect/overhaul the oxygen masks need to ensure the harness inflates to the specific size required by the manufacture and size the FAA certified it at. When I wrote this same issue up a few years back; [Company] disregarded my input and informed me that Maintenance inspects the mask a minimum of every six days. Unfortunately; Maintenance only removes the mask; and ensures the mask inflates within two seconds. Maintenance does not ensure that mask inflates to a specific size; or even fits over their head. I believe that Maintenance should inspect the two-piece oxygen masks to ensure that the harnesses inflate to the specific certified size. The three overhaul companies at the time did not verify the oxygen harness inflated to a set size. I am not sure if they do this today. If not; I question why this is not being done. If recent training is any indication; pilots are more likely to have a depressurization event than a V1 cut. I would request the specified distance from the soft rubber on the mask to the back of the harness; so I can know exactly if I should have the mask replaced. I would rather not be 'that pilot' that writes things up that do not need to be fixed. Since my first write up; I remove my mask every flight in non-compliance with the AOM; but was told I was allowed per the Check-Airmen I have asked. I have written up the harnesses numerous times to have them replaced. I am writing this [report]; as this is the second mask I had to replace in my last two pairings.

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.