Wildfires and Breathing Gas Quality

Dive shops and divers are asking an important question: Will the smoke from wildfires contaminate breathing gas?

With fires raging once more in Canada, Italy, Greece, the U.S., and elsewhere, the Divers Alert Network (DAN) medical and risk mitigation teams have received calls from divers and dive operators concerned about contaminated air.

Similar concerns were raised in 2018, and DAN responded by sending a team to investigate the impact on air quality in and around 17 dive shops ranging from San Diego, California, to Eugene, Oregon, all exposed to wildfire smoke. The findings? No apparent increased risk to divers was found as a result of the smoke from forest fires.

Using both environmental air and compressed air analyzers, DAN’s team of dive safety and medical professionals analyzed concentrations of carbon monoxide (CO), carbon dioxide (CO2), and particulate matter in the air near the dive shops and the fires as well as in recently filled scuba cylinders.

The EPA determines safe air by calculating the air quality index, or AQI, based on CO, CO2, and particulates. In the case of wildfires, the CO and CO2 concentrations lessen dramatically with distance. However, the amount of particulate remains of great concern, even at significant distances.

What the team found was reassuring — when the air outside was analyzed, even when smoke was present and particulate levels were unacceptably high, the handheld monitor did not show elevated environmental levels of CO or CO2.

The next step was to analyze the air in recently filled scuba cylinders. Particulates in compressed air are not easy to detect with any degree of accuracy outside of a laboratory. These are usually effectively removed by properly maintained compressors to levels far below the EPA limits of concern. If concerned, divers can simply smell the compressed air since the human nose can detect the presence of particulates in very small quantities.

In most cases, the team found that dive store owners were using filters which included a catalyst called Hopcalite. This chemical causes CO to convert to CO2 in the presence of gases containing oxygen (such as air). As an additional safeguard, none of these owners were filling cylinders on extremely smoky days. Some operators filled their storage banks on clear days so that they could continue to fill cylinders even when the AQI was unacceptably high.

The level of safety awareness shown by the dive operators, most  of whom had adapted their practices to assure safe air and safe diving for their clients, remains commendable.

While compressed air quality appears to be  unaffected, the reality for dive operators in the areas hit by increasingly frequent and brutal wildfires is that they face other issues besides air quality. Many have to relocate to new dive sites far outside affected areas as regular sites have either burned or been closed due to fire danger or poor quality of the environmental air. Some have to close temporarily until the fire danger passes.

Some dive operators check websites such as fire.ca.gov before planning dives so they can cancel or switch dive sites. Some will close shop because of heavy smoke, while others worry about the long-term effects of the fire on their businesses.

In conclusion, air quality in scuba cylinders should not be compromised as a result of smoke visible in the surrounding areas, even when it can be detected by the human nose. Dive operators should maintain their compressor and filtration systems appropriately, utilize filters fitted with CO removal agents, preferably draw air from inside their buildings, and heed basic safety practices when it comes to fires in close proximity.  

Concerned divers can ask whether the filling station uses CO removal agents and smell their air before diving to be sure there is no residual particulate matter.

For more information, call the DAN Risk Mitigation information line at +1-919-684-2948, or send an email to