Thanks for the actual examples. I spoke to the engineers in JFK today and they said the FAA no longer allowed oxygen bottles to be charged so if the O2 level is low they have to replace the bottle! Apparently it is still allowed in the UK but my company chooses to replace bottles rather than take the risk of an O2 fire.
As long as I've worked on large passenger aircraft oxygen systems [40+ years] I only remember there being two minor incidents and they were both down to [charging] equipment failure. Now whether that was down to the equipment just failing or not being checked properly prior to use I cannot say. On both occasions though the fire was contained on the oxygen charging rigs and didn't spread to the actual aircraft.
At the end of the day I think the main reason for the good safety record in the particular large UK airline in question is down to the fact that the charging of oxygen systems was left to staff who were basically instrument/avionic types, who all had training on oxygen charging, were more likely to have only clean tools [and overalls
] and the oxygen charging cylinders and steps were kept in [and returned to after use] a separate oxygen charging area on the engineering base and were only used for that purpose. It is a sad fact in the industry that there has long been the opinion that separate Engine/Airframe and Avionic trades are not required any more and that all engineers in the future should be B1 and B2 combined. While you may get away with that at line stations there is still the need for separate specialists at main bases/hubs but like everything it all boils down to costs.
In all the years I've worked on aircraft, FAA aircraft have never allowed on board charging as I worked on a number of US/FAA registered airliners back in the 1980s on major checks and they had no charging points.