(c) 2004 by ALBERT DONNAY
All CO-Related Disorders Share Biomarker:
Elevated Level of CO in End-Tidal Breath
uNormal bCO (maximum after holding breath 20 to 25 seconds)
       Healthy Relaxed Non-Smokers                    = 0-2 ppm
uMildly Elevated bCO
Borderline Abnormal for Non-Smokers       = 3-4 ppm
uModerately Elevated bCO 
Smokers and People with CO Disorders     = 5-24 ppm
uHighly Elevated bCO
Recently Smoked or CO Poisoned              = 25-999+ppm
uAll healthy adults have approx. noon peak and midnight trough.
uHigher after supplemental oxygen & if standing vs. sitting vs. supine.