Brought to my attention......
Carbon Monoxide Toxicity: Background, Pathophysiology, Epidemiology
CO is eliminated through the lungs. Half-life of CO at room air temperature is 3-4 hours. One hundred percent oxygen reduces the half-life to 30-90 minutes; hyperbaric oxygen at 2.5 atm with 100% oxygen reduces it to 15-23 minutes.
https://www.google.com/url?sa=t&rct...de.PDF&usg=AFQjCNGZFy4b-E6mL1iwUId_Ifmk3z3WFg
Carbon monoxide is eliminated unchanged via the lungs. The decline in COHb concentration
depends on the rate of carbon monoxide release from haem proteins, alveolar ventilation, oxygen
concentration in inhaled air, duration of carbon monoxide exposure, and the level of COHb
saturation. The formation of COHb is a reversible process, but because of the tight binding of carbon
monoxide to haemoglobin, the elimination half-life while breathing room air is 2–6.5 hours depending
on the initial COHb level. The elimination half-life of COHb is much longer in the fetus than in the
pregnant mother (1–3, 28).
If the levels are low, so is the toxicity rate. Therefore I believe the levels of sypmtoms as the toxicity increases are much more likely to be pronounced for longer periods of time. Be aware that on a boat there can always be a presence....so if any of the symptoms are present, expose the boat to fresh air and reduce any possible source. CO can be deadly, but usually to the totally unaware.