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Standardization of cab air quality: Understanding CO2

Updated: Apr 6, 2022

It had been two years of contemplation, discussion, research, debate, and finally, consensus. The topic was CO2 in operator enclosures. The opportunity to address the effects of CO2 in an operator enclosure through an international consensus standard was exhilarating and humbling. The future of operator enclosure design would be impacted by the outcome of the discussion.

As the project lead for ISO 23875:2021, I was learning that facts are important as is a willingness to be vulnerable. With an admission that we did not fully understand CO2, we worked to develop the facts and the trust necessary for consensus to be reached.

What impact does CO2 have on an operator? Medical science is familiar with CO2 and its effects. Various engineering organizations, NASA, and universities have studied the impact of higher than normal CO2 levels on human cognitive ability and human health. The effects, which range from disorientation, impaired sight, and hearing, to severe headaches and death, have been researched and written upon for some time.

We started the process of reviewing the various research papers and concluded that we did not have research on underground mining CO2 levels. Given the standard would apply to underground mining, we would need to understand how much CO2 is found in various locations within an underground mine environment. The industrial hygienists on the working group set up an ad hoc committee to do the underground testing necessary to address our curiosity and help give direction to our discussion.

The consensus decision was to establish two CO2 levels that would result in an alarm state. The lower level alarm limit added the ambient level of CO2, which is specific to a particular location, to the operator-generated CO2 of 400 ppm.

CO2, ISO 23875:2021, Cab air quality, Air quality
Courtesy of NASA Office of the Chief Health & Medical Officer (OCHMO)

The second alarm level (high alarm) was easy to determine. The internationally recognized CO2 exposure limit is 5000 ppm for an 8-hour work shift. Industrial hygiene practice is to make 50% of the exposure limit, in this case, 2500 ppm, the level at which action must be taken to mitigate the CO2. This is commonly referred to as the "action level".

Why are we rehearsing all of this? As other standards are developed, which include the regulation of CO2, it is essential to learn from the work of others on whose shoulders we stand. Much is lost when those who have labored to come to a consensus in previous standards efforts are asked to render an opinion or give a quick answer without being given time to explain "how we got here." For those more recently on the path, it is wise to recognize the worn-out boots and faded backpacks of those who have gone before. Gordon Covey, of Franklin Covey fame, said it this way, "seek first to understand and then to be understood."

We hope to inform and provoke a conversation with our readers and learn what interests them.

Please leave a comment


Great information. Very thought provoking. Is there a chart that correlates CO2 ppm to percentages?


Thank you, excellent information.

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