Question about heater?

I live in a fairly new two story house. We have just turned on the heater again for night time because it has started to get cold. I believe theres a furnace upstairs in the attic? We hear it start up, then maybe 20 seconds later, air starts blowing from our vents throughtout each room through the ceiling vents. Ive read up on carbon monoxide poisoning and im just so worried that i will fall asleep at night and not wake up! How can I tell if theres something wrong if I cant even get up into the attic in the first place? Would carbon monoxide even be present with my heating situation? By the way, not sure the name of the heating/cooling system....Our air conditioning unit is outside and also controlled by the same thermometer....help give some peace of mind?