In a self-initiated study, the user monitored carbon dioxide levels within their 2025 Ford Explorer ST and found that levels surged significantly when the air conditioning was in use, even with the fresh air selection active.

In the world of automotive innovation, the focus has often been on horsepower, charging speeds, and temperature control. However, a discovery by Lars Remsen, the owner of a 2025 Ford Explorer ST, has shed light on an overlooked aspect - the air quality inside vehicles.

Remen's air-quality sensor, designed to measure CO2, temperature, and humidity levels, revealed a surprising truth during a recent 7-day road trip. With three people in the vehicle, CO2 levels rose from around 400 PPM (ambient level) to over 1600 PPM in less than 10 minutes when the climate system was set to AUTO.

The Explorer's climate system, engineered for temperature efficiency, fan noise, and vent output, often overrides the fresh air selection in favour of recirculation during hot weather. Even when the fresh/recirculate setting was on fresh, the system was recirculating air. This finding, backed by the repeatability of Remen's test results, gives this discovery some weight.

The importance of air quality in vehicles, beyond temperature, has been overlooked. CO2 levels can climb to thresholds known to cause fatigue, headaches, and reduced alertness within minutes. Remen's discovery may be the beginning of a new conversation about what modern vehicles assume on our behalf.

To combat this, Remen found that getting fresh air required running the vehicle on manual fan speed and manual vent outlets. This allows for a true fresh air experience, unlike the system's default settings.

Remen is considering a small run of these sensors if there is interest. For more tips and automotive coverage, you can reach Noah Washington, an automotive journalist based in Atlanta, Georgia, on X and LinkedIn.

The next big automotive breakthrough might not come from more horsepower or faster charging. Instead, it could be about ensuring the air we breathe in our vehicles is as clean and fresh as possible.

In a self-initiated study, the user monitored carbon dioxide levels within their 2025 Ford Explorer ST and found that levels surged significantly when the air conditioning was in use, even with the fresh air selection active.