Carbon monoxide (CO) is a deadly contaminant that can enter scuba cylinders. It may be present in the ambient air or generated by an overheated, inadequately maintained compressor. CO may also come from fire or engine exhaust, from a boat or a gas-powered compressor, for example.
The Silent Killer
While some may dismiss CO in breathing air as a minor risk — after all, a toaster can produce CO — it poses a serious danger in diving. As a diver descends, the density of their breathing gas increases, and so does the number of CO molecules inhaled with each breath. It is not the concentration but the partial pressure of CO that affects us. The deeper we dive, the deadlier it becomes.
CO cannot be smelled, tasted, or seen. The only ways to identify it are by observing symptoms, which is dangerously late, or by using detection tools such as a disposable early-warning device or a dedicated CO gas analyzer.
CO Detection Devices
In response to numerous cases of contaminated gas, CO poisoning in divers, and CO intoxication during boat fires, DAN has researched CO detection products for use by the diving community. Divers need detection tools that are affordable, compact, water-resistant, durable, and easy to use.
Two devices with distinctly different applications are available on the market:
Disposable Single-Use CO Detector
A disposable detector is useful if you suspect there might be CO in your cylinder — because of an unpleasant taste or odor in the gas or because you experience post-dive symptoms such as nausea, dizziness, faintness, or a headache. Testing for CO is one way to rule out contamination.
The CO-PRO, a simple and compact single-use tester, is especially practical for divers who prefer not to invest in an analyzer or who have limited space or other travel-related constraints. The CO-PRO is available from various suppliers, and you can contact the manufacturer, Safety Lab Plus, Inc., directly. This tool provides a straightforward way to prevent intoxication or check whether breathing gas has been contaminated.
CO Analyzer
A CO analyzer is a compact, portable, and relatively inexpensive real-time detector with multiple applications. It enables you to check suspicious cylinders as well as monitor CO levels in your liveaboard cabin (or other trip accommodations) and even at home. It’s useful anywhere you might be concerned about fire or elevated CO levels.
An analyzer appropriate for diving applications should be equipped with level alarms and provide precise readings in parts per million (ppm). It should allow you to verify that your scuba cylinder has less than 10 ppm (USA CGA limit) or 5 ppm (European EN limit) or that there is no engine exhaust or combustion product making its way into your cabin or room.
One such device, the FD-103-CO analyzer from Forensic Detectors, offers a product for the prudent but budget-conscious traveler. The analyzer is available from the manufacturer.
Please note that DAN does not endorse specific products. Our intention is to provide guidance about effective CO detection devices for divers concerned about their safety.
For more information about CO, explore these additional DAN resources: