In the US, the FAA required the removal of chemical o2 generators. Now they are requiring o2 back in the lavs. On our planes (737) we are currently installing o2 bottle systems where the chemical generators used to be.
FAA Requires Oxygen To Be Returned To Airliner Lavs | Aero-News Network
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/bfeea008e1a9e61d86257e8f004c247c/$FILE/2012-11-09%20R1.pdf