@heart4wi I measured my husbands carbon dioxide levels by using an oxymeter which you can pick up at most drug stores; ie, CVS, Walgreens, Rite Aid. You may even ask your pharmacist at a local supermarket. It really measures the oxygen in your blood so we all want 100% or as close as you can get to 100% oxygen in our blood. My husbands readings were in the low 50's - 70's and that's because he wasn't able to expell the carbon dioxide out of his body. He would get all loopy and tired, so exhausted to the point he wouldn't wake up and became unresponsive. Point being, if you see a reading as low a 50 - 70, call 911 STAT! Hope this helps. Good luck- betsc