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If there’s one thing we know about SUVs, it’s that they’re better handling vehicles than before and pack more computing power than ever before. But sometimes, the very systems designed to cocoon us can end up surprising us in unintended ways.
Lars Remsen, an owner of a 2025 Ford Explorer ST and a man with a knack for DIY electronics, recently uncovered something that most drivers would never think to measure: the air they’re breathing.
“I have been building air-quality sensors recently, and decided to make a minimalist CO2 / Temp / Humidity sensor before I headed out on a 7-day road trip with my family.
Since these new vehicles are well sealed, there is a potential to build up CO2 inside, which, especially after long exposures, has a long list of symptoms like headache, dizziness, fatigue, anxiety, etc. Not what you want for long hours of driving!
The results were actually pretty shocking. With 3 people in the vehicle, the CO2 levels rose from around 400 PPM (which is the ambient CO2 outside) to over 1600 PPM in less than 10 minutes.
This was with the climate system set to AUTO (2/3) on my 2025 ST. But the wild part was that I had the fresh/recirculate setting on fresh. So, that setting is ignored on AUTO, and it is recirculating! Even switching to manual fan speed, but leaving the air outlets to auto, had the same behavior.
In order to truly get fresh air, you have to run these on manual fan speed and manual vent outlets. Only then does the fresh air setting work. At least during high ambient temps. To make it even worse, if you don’t have the dash (defrost) outlet selected, it defaults to recirculate every time you start it up. The sensor made it super easy to see this at a glance and change the setting.
I might consider doing a small run of these sensors if there is interest. You just plug in USB-C and it’s off and running. It has color coding (green/yellow/red) for the numeric value and the line graph, with time periods on the graph from 2min to 12 hours.
This photo shows just how quickly it rises on AUTO, and also how quickly you can get it back very low with the right settings.”
Remsen dropped this finding on the Explorer ST Owners Facebook group, armed with charts, graphs, and a hand-built USB-C sensor that wouldn’t look out of place in a lab-grade test bench. The vehicle in question wasn’t misbehaving, per se; it was doing what it was programmed to do. But therein lies the rub.
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When the A/C is set to AUTO and the ambient temperatures are high, the Explorer prioritizes cooling efficiency over air exchange, defaulting to recirculation even when the user selects fresh air. The result? Within minutes, CO₂ levels climb to thresholds known to cause fatigue, headaches, and reduced alertness. Not exactly the trifecta you want on a long-haul family road trip.
2025 Ford Explorer ST Performance Trim: Sport‑Tuned Power & Handling
- Ford launched the ST performance trim to inject more sport‑oriented driving dynamics into the Explorer lineup and compete in the performance‑SUV segment
- The ST’s 400 hp twin‑turbo V6 delivers significantly sharper acceleration and higher towing ability vs. the standard turbo‑4 engine
- With sport‑tuned suspension, larger brakes, and styling cues like a black mesh grille and red calipers, the ST aims to deliver a more athletic presence
- The ST option helps attract buyers seeking both family‑friendly SUV utility and enthusiast-level performance in one vehicle
As expected, the Facebook comments were a cross-section of the modern car enthusiast hive mind. Stephen Mitchell reminded the group of the infamous 2011–2015 Explorer cabin exhaust debacle, but others like Richard Haltom were quick to point out: that was CO, this is CO₂. A crucial distinction. One is immediately toxic, the other is subtle, cumulative, and often ignored, until you’re yawning behind the wheel, wondering why you feel like you’ve been locked in a conference room with no ventilation.
The Explorer’s climate system, like most late-model vehicles, is a highly automated affair. According to CyanLabs and explorerst.org, the AUTO setting in Ford’s HVAC logic is engineered to balance temperature efficiency with fan noise and vent output.
It’s not uncommon for the system to quietly override the fresh air selection in favor of recirculation during hot weather.
What Remsen’s sensor proved is that this override has real physiological consequences, even in normal driving conditions. And the kicker? The “fresh” setting isn’t truly fresh unless you run the system in full manual mode, controlling both fan speed and vent direction yourself.
Is This An Important Issue?
Naturally, skepticism followed. Michael DeMarco, another member of the group, brushed off the test as anecdotal:
“I appreciate the time spent on something this mundane… without any sort of control or reproduction of results, it’s all anecdotal.”
But Remsen pushed back hard, noting the results were repeatable throughout his 7-day trip, across a range of conditions.
“Set it to auto… CO₂ immediately begins to rise. Force full manual mode, and it immediately falls. This is very repeatable. Take it or leave it.”
That repeatability gives this finding some weight. In an era where we can summon 400 horsepower with our right foot and get Spotify from the cloud, it’s ironic that something as simple and vital as ventilation could fly under the radar. But here it is, exposed by a $30 sensor and an inquisitive mind. Not a safety recall. Not a scandal. Just a moment of clarity from inside the airtight cocoon of progress.
2025 Ford Explorer ST Specs: Engine, Dimensions & Towing Capacity
- The ST is powered by a 3.0 L twin‑turbo V6, producing around 400 hp and 415 lb-ft of torque, paired with a 10‑speed automatic and available AWD
- Approximately 198.8 in length, 78.9 in width (without mirrors), height around 69.9 in, and wheelbase near 119.1 in
- Curb weight around 4,457 lb, with towing capacity rated up to 5,000–5,300 lb depending on configuration
- Official 0‑60 mph time for the ST version is around 5.2 seconds
Ford hasn’t done anything wrong here; this is modern HVAC strategy in action. Recirculation improves cooling efficiency and reduces compressor load. But in the quest to perfect temperature control, we’ve perhaps forgotten the importance of air quality. It’s not just about temperature; it’s about what you’re breathing hour after hour on the road to Yellowstone or soccer practice.
Remsen’s discovery isn’t the end of the world, but it may be the beginning of a new conversation. As vehicles become ever more automated, sealed, and software-governed, we should be asking not only what our cars do, but what they assume on our behalf. The next big automotive breakthrough might not come from more horsepower or faster charging.
Sources: Ford Media Center
Noah Washington is an automotive journalist based in Atlanta, Georgia. He enjoys covering the latest news in the automotive industry and conducting reviews on the latest cars. He has been in the automotive industry since 15 years old and has been featured in prominent automotive news sites. You can reach him on X and LinkedIn for tips and to follow his automotive coverage.
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Source: torquenews.com
