What is a common cause of carbon monoxide poisoning?

Carbon monoxide poisoning during SCUBA diving is most commonly caused by the intake of exhaust fumes, particularly when a compressor used for filling SCUBA tanks is improperly located. If the compressor's intake is situated close to sources of exhaust, such as car or boat engines, it can draw in these toxic fumes. Carbon monoxide is a colorless, odorless gas that can rapidly accumulate and enter the breathing air, posing a serious hazard to divers.

In diving contexts, maintaining clean breathing air is crucial for safety. When divers inhale carbon monoxide, it binds to hemoglobin in red blood cells more effectively than oxygen, leading to reduced oxygen delivery throughout the body, which can result in symptoms ranging from headaches to life-threatening conditions.

The other options do not directly relate to the cause of carbon monoxide poisoning. High humidity does not contribute to carbon monoxide levels, and while deep water diving and poor diving techniques can lead to other serious diving-related issues, they are not associated with carbon monoxide toxicity.