What’s in Your Air?

Choosing a reputable dive operation with a reliable safety record is important for ensuring your personal safety while diving — even if you rely on them for nothing more than air fills. Having clean air to breathe is one of the basic requirements for sustaining life both above and below the surface, so divers and dive operators alike must be mindful of breathing gas purity.  

Gas purity is of particular importance to divers and the diving industry because hazards relating to air supply contamination increase in severity with depth. Two molecules of particular concern that must be closely and responsibly monitored in divers’ air supplies are carbon monoxide (CO) and carbon dioxide (CO₂).

CO is an odorless, tasteless, and invisible toxic gas, which makes it a problematic culprit for breathing gas contamination due to the ease with which it can infiltrate gas supplies and remain undetected without careful monitoring and prevention. The reason CO is a dangerous molecule is because it binds readily to hemoglobin, which is the primary carrier of oxygen in the blood. With lots of CO bound to the blood’s hemoglobin, the blood’s ability to carry oxygen is diminished, which can cause both immediate and long-term health effects related to oxygen starvation in tissues and organs. 

Elevated levels of CO₂ in breathing gas also pose a significant threat to divers because CO₂ is the most abundant potential contaminant present at fill station locations. CO₂ has many of the same characteristics as CO but is unique in that it has an additional oxygen atom, double bound to the central carbon atom, resulting from complete rather than incomplete combustion. CO₂ is essential to life on earth due to the role it plays in photosynthesis. However, in humans, CO₂ is a byproduct of respiration and is the primary mechanism that triggers breathing in our bodies. Therefore, exposure to elevated levels of CO₂ can result in increased respiration, hyperventilation, dizziness, spasms, unconsciousness, and even death. Therefore, it is important to manage CO₂ in breathing gas to ensure it remains below established limits. 

The challenge that divers face with exposure to CO and CO₂ in breathing gas is that levels of contamination considered to be within safe limits on the surface become very problematic at depth. For example, a CO reading of 10 parts per million (ppm) at the surface would have an equivalent effect of 60 ppm on a person at 50 meters of seawater. This would be dangerous to divers because according to the US Environmental Protection Agency, the maximum short-term exposure level to CO must not exceed 35 ppm, within a one hour time frame, no more than once per year. Evidently, divers must be very mindful of CO and CO₂ risk, as multiple exposures could easily add up to exceed the accepted annual safe levels recommended to avoid CO and CO₂ poisoning or even death.

To manage the risks associated with exposure to CO and CO₂, it is important to consider potential origins and their relative proximity to air compressor intake values. Common sources of both CO and CO₂ overlap, so dive operations can generally manage both issues simultaneously with a comprehensive risk mitigation and hazard identification plan for their air fill stations.  

Potential sources of CO and CO₂ air source contamination include: engine exhaust from cars, boats, and generators; smoke from cigarettes and fires; biomass accumulation from waste dumps, fertilizer piles, or compost operations; nearby storage of pesticides, paints, cleaning supplies, and fuel; and close proximity cooking areas, building sites, ventilation outlets, or effluent discharge locations.    

As a consumer, it is important to perform a background check on prospective dive operations to gain insight into their risk mitigation procedures and policies specifically relating to cylinder fill stations. Transparency and acknowledgement about where intake and output values are located relative to these potential sources is essential for finding a reputable dive business who will work to keep you safe on your next diving adventure.