What primary activity can increase a diver's carbon monoxide level apart from a contaminated air source?

Smoking cigarettes is the primary activity that can increase a diver's carbon monoxide level aside from using a contaminated air source. When a person smokes, they inhale various harmful chemicals, including carbon monoxide, which is produced through the burning of tobacco. This gas can bind to hemoglobin in the blood, reducing its oxygen-carrying capacity and subsequently impairing a diver's ability to safely oxygenate their body during dives.

The harmful effects of carbon monoxide are particularly concerning underwater, where available oxygen levels are already lower than on the surface. When divers smoke, they can inadvertently introduce carbon monoxide into their bloodstream, which can lead to serious health risks, including impaired cognitive function and increased risk of decompression sickness. This makes it vital for divers to avoid smoking, especially before or during diving activities.

In contrast, while exercising before a dive can increase a diver's overall oxygen demand and potentially produce carbon dioxide, it does not significantly elevate carbon monoxide levels. Eating heavy meals may lead to discomfort or reduce buoyancy but does not directly impact carbon monoxide levels. Using dive tanks with low oxygen presents risks, but it does not involve an increase in carbon monoxide specifically. Thus, smoking remains the most relevant activity concerning increased carbon monoxide exposure in divers.