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Carbon Monoxide Poisoning in Diving

CO poisoning is often referred to as the 'silent killer' in scuba diving because you can't smell or taste it but several divers die from it every year.

This guide lists the common causes and symptoms of Carbon Monoxide (CO) Toxicity and what steps divers should take if they get poisoned during or after a dive.

Carbon Monoxide Toxicity: Common Causes

This invisible toxic gas is odourless (so it doesn't smell) and tasteless.

It can cause permanent brain damage and may be fatal if not quickly detected and corrected. The poisonous chemical can come from:

The Environmental Protection Agency (EPA) suggests that exposure to more than nine (9) parts per million (ppm) during any given eight-hour period can be harmful.

Here's the thing:

Let's say you make a scuba dive using a 12 litre dive cylinder filled with air to a depth of forty (40) metres. It's fair to assume that the compressed air would have been drawn at sea level with a value around five (5) ppm.

During the actual dive, the surface equivalent value (SEV) would produce a similar effect as breathing twenty five (25) ppm at the surface.

In other words, making multiple dives could expose scuba divers to levels above the accepted safe limits of carbon monoxide (CO).

Carbon Monoxide Poisoning Symptoms

It may take more than an hour for carbon monoxide to show. This is because the toxin slowly replaces vital oxygen in the bloodstream - eventually starving the heart and brain.

As a result, the typical signs and symptoms of carbon monoxide sickness in scuba diving will include:

How to Treat Carbon Monoxide Sickness

Special Considerations

It's important for scuba divers to be aware that you can be suffering the toxic effects of carbon monoxide toxicity and not show any obvious signs or symptoms.

Related Information and Help Guides

Important: The tutorial video [16:21 seconds] presented by DAN explains how gas toxicities and pressure affect the human body during a dive.

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