Narrative:

In cruise on autoplt at 28000. The first officer left to use the lavatory. I donned oxygen mask completely. After several mins, I removed headband from my head and held mask to my face with 1 hand. After a min or so, FAA inspector requested I replace the headstrap, and I did. Kept mask on until first officer returned to his seat. Rest of flight normal.

Google
 

Original NASA ASRS Text

Title: A WDB CAPT WAS TOLD BY AN ACR INSPECTOR TO PUT HIS OXYGEN MASK ON PROPERLY WHILE THE FO WAS OUT OF THE COCKPIT.

Narrative: IN CRUISE ON AUTOPLT AT 28000. THE FO LEFT TO USE THE LAVATORY. I DONNED OXYGEN MASK COMPLETELY. AFTER SEVERAL MINS, I REMOVED HEADBAND FROM MY HEAD AND HELD MASK TO MY FACE WITH 1 HAND. AFTER A MIN OR SO, FAA INSPECTOR REQUESTED I REPLACE THE HEADSTRAP, AND I DID. KEPT MASK ON UNTIL FO RETURNED TO HIS SEAT. REST OF FLT NORMAL.

Data retrieved from NASA's ASRS site as of July 2007 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.