Helium and oxygen tanks cannot be recycled in your curbside recycling and they are hazardous when placed in the trash.
Check with your medical equipment supplier to see if they have a take-back or exchange program for the oxygen tank. Medical supply companies will accept an oxygen tank if you purchased the tank from them.
Recycle at a local scrap metal yard (you may earn a rebate) or contact AAA Gas Supply (216.228.4800), Air Gas Great Lakes (216.241.1696) or Recycle Zone (440.471.4652) for recycling options. Otherwise, save for your community's next household hazardous waste collection event.