Are Eco settings on cabin ventilation systems a safety hazard?

[GRA]

Unsure where to put this, so mods feel free to move it elsewhere if you think that's a better fit. Via GCR: http://www.greencarreports.com/news/1111361_are-eco-settings-on-cabin-ventilation-systems-a-safety-hazard

As corporate average fuel economy requirements that started in 2012 continue to tighten, automakers have turned to an entire arsenal of tactics to reduce the fuel their vehicles burn. . . .

One of the less-discussed methods is the "Eco" button offered in increasing numbers of new cars, which reduces the car's available power and minimizes accessory use. Among the many vehicle systems an Eco setting can affect is the car's heating, ventilating, and air conditioning system, known by the acronym HVAC.

Now, in an article published by the Society of Automotive Engineers, one vehicle engineer has suggested that reduced ventilation inside new vehicles could potentially lead to dangerous buildup of carbon dioxide, slowly imperiling occupants. One state transportation department has specifically cited excess carbon-dioxide levels in the blood of more than one driver who was killed in vehicle crashes, taking the problem from the theoretical to the documented.

Released in April, the article notes that for many years, even the "recirculate" setting on a car's HVAC system let in a small amount of fresh air via a notch in the outside air-flap door that closed off the system. In previous decades, car bodies were relatively leaky and fan blowers often didn't completely switch off, meaning that at least some fresh air was continually admitted to the cabin. With strenuous efforts to reduce aerodynamic drag and energy draw, vehicle doors are now triple-sealed and certain HVAC settings permit the fan to be entirely switched off, effectively eliminating any fresh-air ingress. . . .

A presentation at the 2017 SAE World Congress technical meeting by G.D. Mathur, a test and development engineer at Calsonic Kansei North America, offered more details. It noted that EPA limits on short-term carbon dioxide exposure were intended only as safety measures when carbon dioxide is used as a refrigerant in vehicle air-conditioning systems—and were not written to consider the effects of CO2 built up from human breathing. . . .

Mathur's modeling suggested that carbon dioxide could build up to 1100 parts per million—slightly over the comfort limit of 0.1 percent of cabin air—in as little as 4 to 5 minutes of a simulated test drive. An eight-hour road trip without stopping could thus raise carbon-dioxide levels to hazardous concentrations. Indeed, the Arizona Department of Transportation has attributed several crash deaths to excessive CO2 buildup in drivers. Post-mortem blood analyses validated the diagnosis, taking cabin buildup of carbon dioxide from a theoretical issue to an actual safety hazard. . . .

 

[user 10599]

Interesting article. I will have to show this to my wife. She balks at how one of my cars turns the recirculate off after a bit of driving and then she can smell the fumes from the other traffic. I tried explaining it was a safety feature but she insisted it was a defect.

 

[LeftieBiker]

I can't think of any car other than a Prius or similar hybrid that would have both an "Eco" setting and an ICE... and I don't think the Leaf's interior volume is small enough to make CO2 a particular hazard unless the car is full of people.

 

[TomT]

Recirculate does not totally shut off outside air on any car that I am aware of (partially by design and partially due to leakage in the system and vehicle)... It is typically about an 80/20 mix...

 

[GRA]

Recirculate does not totally shut off outside air on any car that I am aware of (partially by design and partially due to leakage in the system and vehicle)... It is typically about an 80/20 mix...

The article also included this statement:

Moreover, automakers can earn a small credit on the CAFE scores for any vehicle that entirely shuts off the fan on its maximum air-conditioning setting, which slightly reduces its energy usage.

So I'd say this is definitely coming if it's not already here, unless it's outlawed for safety reasons.

 

[TomT]

I suspect that setting is rarely if ever used in practice as it would be impossible to get much air moving in the car or through the evaporator without the fan... Perhaps they are referring to the condenser fan which is not usually necessary at speed instead...

The article also included this statement:

Moreover, automakers can earn a small credit on the CAFE scores for any vehicle that entirely shuts off the fan on its maximum air-conditioning setting, which slightly reduces its energy usage.

So I'd say this is definitely coming if it's not already here, unless it's outlawed for safety reasons.

 

[LeftieBiker]

Yeah, that statement is garbled. It makes no sense whatsoever to have no ventilation fan running on the A/C's "maximum" setting. The evaporator would just get very cold and ice up, while the cabin stayed hot.

 

[SJEVer]

I can't think of any car other than a Prius or similar hybrid that would have both an "Eco" setting and an ICE... and I don't think the Leaf's interior volume is small enough to make CO2 a particular hazard unless the car is full of people.

Now that small portable CO2 monitors are available, I can see CO2 readings >3,000 in my 2019 Leaf if I am driving with windows closed and CC on recirculate, with just 2 people in the car. Yes, hazardous levels that can make you drowsy!

 

[SJEVer]

Unsure where to put this, so mods feel free to move it elsewhere if you think that's a better fit. Via GCR: http://www.greencarreports.com/news...-on-cabin-ventilation-systems-a-safety-hazard

Now that small portable CO2 monitors are available, I can see CO2 readings >3,000 in my 2019 Leaf if I am driving with windows closed and CC on recirculate, with just 2 people in the car. Yes, hazardous levels that can make you drowsy!