where to sell my old Cpap machine

You're absolutely right, which is why I wrote the cautionary last paragraph above.

 It worries me too when people do not use their CPAP properly. I would hope anyone needing CPAP would get it through the proper channels, learn how to use it correctly and have on-going monitoring of its use and their condition. At the very least, I would hope that if someone has no way to afford a  CPAP machine other than to buy second hand, that they would at least go through their medical team to have the machine properly calibrated and their use of it monitored by appropriate professionals.  

Unfortunately, even many people who post here that they've been told they need CPAP don't seem to understand just how serious sleep apnea is and how important their compliance is for their health.

Any other suggestions of how the machines could be properly recycled and gotten to those that need them would be very welcome!

Try these places, or someplace like them if you don't want to donate it.

http://cpapbuyers.com/

http://www.secondwindcpap.com/

You should find out if there is a donation site for the poor/uninsured in your area. They are usually DESPERATE for those machines. We found out about it through the sleep specialist that prescribed it for my husband.