Do Wildfires Affect Breathing Gas?

After a hot, dry summer, fires are ravaging parts of California, Washington, Oregon and elsewhere. Seeing the spread of fire and smoke, area divers and dive operators are asking an important question: Will the smoke from the West Coast wildfires contaminate breathing gas?

When the region suffered wildfires in 2018, divers expressed similar concerns to DAN, and DAN responded by sending a team to investigate the impact of the smoke on air quality in and around 17 dive shops ranging from San Diego, California, to Eugene, Oregon.

The findings? No apparent increased risk to divers was found as a result of the smoke from the forest fires.

Using both environmental air and compressed air analyzers, DAN’s team of dive safety 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 Environmental Protection Agency (EPA) determines air safety by calculating the air quality index (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 particulates 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 that 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 in 2018, most of whom had adapted their practices to ensure safe air and safe diving for their clients, was 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. This year, operators have had 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 air quality. Some operators have closed temporarily until the fire danger passes. Cal Fire, and other like-minded sites, can help dive operators get accurate information so they can plan ahead and switch dive sites as necessary.

This year, however, the fire season is coinciding with the COVID-19 pandemic, causing even further economic hardships.

However, for those still able to dive, air quality in scuba cylinders should not be compromised as a result of smoke visible in 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 nearby fires.

Concerned divers can ask whether the filling station uses CO removal agents and should smell their air before diving to be sure there are no residual particulates present.