What is the effect on the O2 affinity of hemoglobin? An increase in CO from 1.0 parts per million(ppm) in a normal indoor atmosphere to 30 ppm in a home that has a malfunctioning or leaking furnace.

With this one I am unsure. Is this answer increase in oxygen affinity of hemoglobin because carbon monoxide bound to one site in hemoglobin will shift the oxygen saturation curve of the remaining sites to the left, resulting in an increased affinity for oxygen, or would it be a decrease in oxygen affinity for hemoglobin because carbon monoxide binds to hemoglobin tighter to hemoglobin than oxygen?