FAQ: What is the difference between Ambient CO levels and COHb levels?

Short Answer: Ambient air levels refer to the amount of carbon monoxide in the air you are breathing (indoor air), expressed in terms of PPM (parts per million.) COHb levels represent the amount of carbon monoxide which is in the blood, from having breathed high ambient air levels of CO. COHb is short for carboxyhemoglobin.

From our video podcast series with Gordon Johnson and Griff Winthrop.

What is the difference between Ambient CO levels and COHb levels? Ambient levels = levels in the air you breathe (typically in indoor air) and COHb is of carbon monoxide concentration in blood, expressed in a percentage.

Gordon Johnson: Back to frequently asked questions. What is the difference between Ambient CO levels and COHb levels? And then we’ll talk about the difference between ambient air levels in the room and exhaust CO levels. So what’s the difference between COHb carboxyhemoglobin level and ambient air levels?

Griff Winthrop: Well, first of all, it’s how they’re expressed. COHb is expressed as a percentage and ambient is expressed as parts per million. You also see that often see that as PPM and it just like it sounds. Ambient levels are the amount of carbon monoxide in parts per million in the air that you’re breathing.

Gordon Johnson: So ambient means the air that we breathe, the atmosphere we’re in.

Griff Winthrop: Yes. If you look here and we’re in my office on the second floor of my barn, If somebody were to crank up my tractor right now and let it run the ambient levels in the air that I’m breathing right now would, would climb from zero to  something that I don’t want to be involved with. Right. So it is the air. Everything that you see behind me is is my office. And the air that I’m breathing is the ambient air.

Gordon Johnson: How do you know that the air in your office is zero?

Griff Winthrop: Well, because I’ve got a carbon monoxide alarm. It’s digital.

Gordon Johnson: I know that the air in where I’m sitting right now is zero, because I have my Forensics Carbon monoxide, portable alarm, and it says zero.

COHb levels are the levels of carbon monoxide in a person’s blood, after they have been carbon monoxide poisoned.

For more information on the what is the difference between Ambient CO levels and COHb levels, see a paper from the American Lung Association, published at: https://afdc.energy.gov/files/pdfs/2781.pdf#:~:text=But%20if%20air%20in%20the%20lungs%20contains,to%20body%20tissues%20by%20the%20remaining%20oxyhemoglobin 

See also https://www.epa.gov/indoor-air-quality-iaq

However, be warned that most of the .gov resources with respect to carbon monoxide are being deleted from the federal governments data basis.