Narrative:

Shortly after entering nat V; one of our first class flight attendants (flight attendant) called the cockpit to notify us of strong fumes emanating from lavatory 101 (first class inboard lav) directly behind the cockpit. I stepped back (using SOP security protocols) to investigate and immediately smelled a strong chemical odor which I could not identify. It was a cross between iodine; chlorine and some kind of disinfectant. In a matter of 1 minute; I had a sore throat and headache. I immediately returned to the cockpit; donned O2 mask; and asked the purser to see if the fumes were anywhere else in the cabin. Specifically checked every other lav on the aircraft; with no trace of the odor. The odor was localized to lav 101; with occasional whiffs finding their way into the cockpit. Contacted dispatch and [maintenance]; and followed all suggestions and recommendation; but odor did not diminish.I discussed the problem and options with the pilot flying and international relief officer; and sent international relief officer back to further investigate. He returned in about 5 minutes and reported feeling very nauseous. At this point I made the determination to divert; because there was not enough O2 to continue to destination; the source and nature of the noxious fumes was unknown; and we already had some negative physiological effects.put entire crew on O2 and diverted to the south off nat V following all sops (altitudes; exterior lights; transmitting in blind; etc.). International relief officer initially had difficulty communicating with ATC to coordinate clearance to ZZZZ. Descended to FL300; picked up IFR clearance to ZZZZ; used diversion checklist and landed uneventfully at ZZZZ. Crew O2 was 1760 psi at preflight; 470 psi on landing.ATC (and customs when they came aboard the aircraft several hours after landing) told us that [police] had been alerted that we were diverting because there was a suspect item on board; but we had not reported any such issue.contract maintenance checked lav 101 thoroughly; and could not find the source of the fumes (which also affected the maintenance technician.) we washed down the lav top to bottom; including inside all cabinets and behind all doors and panels. The odor was almost gone; and was not emanating as before. Discussed with dispatch and [maintenance]; and opted to return to [the departure airport]. Did so uneventfully. Amt that came on board could smell slight traces of the fumes after aircraft was deplaned; but could not identify what they were.also of interest was the presence of two punctured holes in the forward wall of lav 101. I do not know whether they were present before departure; but in retrospect; I wonder if (however unlikely) this incident might have a security component to it; in terms of bringing a small amount of a volatile compound on board; breaching the cockpit wall; and incapacitating the pilots with the fumes.

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Original NASA ASRS Text

Title: While flying in Oceanic airspace; a Boeing 777 flight crew was made aware of a strong chemical odor coming from one of the forward lavatories. As the source of the odor could not be readily determined the crew elected to leave the Oceanic track and divert to a suitable airfield.

Narrative: Shortly after entering NAT V; one of our first class Flight Attendants (FA) called the cockpit to notify us of strong fumes emanating from Lavatory 101 (First Class inboard lav) directly behind the cockpit. I stepped back (using SOP security protocols) to investigate and immediately smelled a strong chemical odor which I could not identify. It was a cross between iodine; chlorine and some kind of disinfectant. In a matter of 1 minute; I had a sore throat and headache. I immediately returned to the cockpit; donned O2 mask; and asked the Purser to see if the fumes were anywhere else in the cabin. Specifically checked every other lav on the aircraft; with no trace of the odor. The odor was localized to Lav 101; with occasional whiffs finding their way into the cockpit. Contacted Dispatch and [Maintenance]; and followed all suggestions and recommendation; but odor did not diminish.I discussed the problem and options with the Pilot Flying and IRO; and sent IRO back to further investigate. He returned in about 5 minutes and reported feeling very nauseous. At this point I made the determination to divert; because there was not enough O2 to continue to destination; the source and nature of the noxious fumes was unknown; and we already had some negative physiological effects.Put entire crew on O2 and diverted to the south off NAT V following all SOPs (altitudes; exterior lights; transmitting in blind; etc.). IRO initially had difficulty communicating with ATC to coordinate clearance to ZZZZ. Descended to FL300; picked up IFR clearance to ZZZZ; used Diversion Checklist and landed uneventfully at ZZZZ. Crew O2 was 1760 PSI at preflight; 470 PSI on landing.ATC (and Customs when they came aboard the aircraft several hours after landing) told us that [police] had been alerted that we were diverting because there was a suspect item on board; but we had not reported any such issue.Contract maintenance checked Lav 101 thoroughly; and could not find the source of the fumes (which also affected the maintenance technician.) We washed down the lav top to bottom; including inside all cabinets and behind all doors and panels. The odor was almost gone; and was not emanating as before. Discussed with Dispatch and [Maintenance]; and opted to return to [the departure airport]. Did so uneventfully. AMT that came on board could smell slight traces of the fumes after aircraft was deplaned; but could not identify what they were.Also of interest was the presence of two punctured holes in the forward wall of Lav 101. I do not know whether they were present before departure; but in retrospect; I wonder if (however unlikely) this incident might have a security component to it; in terms of bringing a small amount of a volatile compound on board; breaching the cockpit wall; and incapacitating the pilots with the fumes.

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.