Do you have them in your home?
My parents got carbon monoxide poisoning today. They were very lucky that I got to them in time. They called complaining about headaches and my dad was dizzy and having trouble standing. I walked into the house and could smell gas. My mom was crawling on the floor crying and my dad looked like a ping pog ball walking trough the hallway. Just the little time I was in there I was having trouble breathing. I called 911. Had my mom crawl to the door for fresh air and then helped my dad. I got a little carbon monoxide in my system while trying to help them. We're all fine. My parents were taken to the er for extra oxygen. My parents ended up having a gas leak also.
I encourage everyone to service your furnaces and get a carbon monoxide detector.