Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Interior Re-circulated air

My wife is extremely sensitive to smells, like car/truck exhaust fumes, tar on road, gasoline, and many other smells in the outside air, so we are candidates for a car that recirculates the interior air and does not pull from the outside when the heater or air conditioner is used. We would appreciate any recommendations as to what to buy; we have heard Japanese cars excel in recirculating the interior air (Honda Acura, Honda other?); is this true? Are there any other models anyone would recommend? And are there models that recirculate interior air all the time, or does one have to activate a switch to shut off outside air (or bring it in)? We looked at a new Lincoln MKZ and the salesperson mentioned that the car has a switch to cause interior air to recirculate, and it also has a filtration system. He indicated the filter must be changed every so many miles. Is his information reliable, or is he just trying to make a sale?

Appreciate any responses!

The assumption of variation by make is a complete new one on me. All vehicles have a recirc position for the HVAC system, and I really can’t imagine that its performance varies much by make. This sounds like another “Japanese cars are better…” urban legend to me.

The cabin air filter bit (mentioned re: the Lincoln) might make some difference, but its real job is to filter outside air. So if you want to recirc it may make some difference, but that’s not its real point. On that note, many cars have these.

I’m actually posting to make a very practical suggestion. Whenever you go to look at a car bring some kind of innocuous odor producing device that your wife enjoys the smell of. Spray some around in the area of the base of the windshield while she sits in the car with the fan running on recirc. Compare cars for smell. A little field testing is always a good bet.

Every car I have owned had a recirculate option, the problem with recirculate is in the winter it does not displace moisture so you are very prone to fogged windows. There are cars with exterior filters for the air that do better than those without, but as far as recirculate goes I think you will find many cars with that option. In all the cars I know the filters are not good enough to provide the level of filtration it sounds like your wife needs, short answer, the Lincoln is not the only choice.

Uh, if it didn’t pull any outside air at all, wouldn’t you eventually die?

But cars that are equipped with air conditioning can be set to “recirculate” mode where something like 90% of the air is recirculated, either by setting them to “Max AC” or these days especially there’s usually a separate switch or button for it. (That for a long time the Japanese cars had “recirc” buttons while domestics just automatically recirculated when on max AC may be why you’ve heard they’re good for this). Short of some really high-tech stuff that comes on Rolls Royces and Bentleys and the like, I think all cars are pretty much the same in terms of outside air circulation.

But for your wife’s issue, you just need to make sure you get a car with a cabin air filter and make sure you have a HEPA-grade filter in place.

Some outside air MUST be brought into the interior of a car or the trapped inside air gets “polluted” quickly enough…High moisture levels and CO2 levels and diminishing oxygen levels make for an uncomfortable ride…

You need to learn the symbol for recirculating air so you can see for yourself which cars have this feature. I think pretty much all cars have a way to recirculate the air.

Most, but not all, have cabin air filters too.

The MKZ salesman wants to sell cars, but he is telling the truth on this occasion.

I agree, and would add that the cabin filter may be as important as any other feature. If you find the filtration system is superior in on car over another, that would be worthwhile, though I doubt it’s an issue. Personally, I would talk to HC professionals and their recommendations along those lines. Ambulance service providers “may” have a recommendation or considerations.

A lot of cars today have cabin air filters. The stock filter media can often be replaced with a true HEPA filter. The downside is that you’ll end up changing the filter more often and it’ll be more expensive than a stock filter. However, if you have special needs, this is the way to go…

Most vehicles have a provision to recirculate interior air, but it’s NEVER 100%. There is always some exterior air being brought in. Vehicle interiors are not airtight. There is no way to keep all exterior air out of the cabin, no matter what anyone tells you.

A vehicle with a really good cabin air filter may help your situation, but that’s the only thing I can think of.

What are you driving now?

John Deere advertises their tractor cabs block pollen infiltration with filtration and use cabin pressure to help minimize the effects of leakage. Maybe cars could learn something here. They work in really bad environments and have tried to answer the call.

All cars let some outside air in when you use recirculate mode. None of them are perfect, and they all have a recirculate mode for the air conditioner. Some have a “recirculate” symbol, and some refer to the mode as “max,” but they do the same thing.

If your wife is sensitive to smells, I suggest you google “new car outgassing” and find a model that doesn’t leach as many toxins as the worst offenders. I believe this will be more important to the health and well-being of your wife.

Find a model that doesn’t outgas and has a cabin air filter, and I think she might be happy.

I remember well the old days where car heaters were boxes under the dsshboard that contained the heater core and a fan. These heaters recirculated the inside air. It seemsed that no matter how big the manufacturer made the heater core, the car was always cold. An engineer, Nils Eric Walberg, who worked for Nash found that when the car was in motion, the pressure outside the car was greater than the pressure inside the car. Air would infiltrate everyplace. His solution was to pressure the passenger compartment b bringing in outside air and heating it. Nash called this system “Weather Eye” and was adopted by all manufacturers. Heating outside air actually keeps the passenger compartment warmer. The recirculate mode still brings in some outside air to keep the passenger compartment pressurized.

There used to be a problem with where the air intake was located. On some cars, it was just above the front bumper. After a lawsuit against Buick where a person was killed by exhaust fumes while sitting with the heater running behild another running car, manufacturers moved the air intake up under the windshield. The air intake has been here for more than 50 years.

I find the air filter on my present vehicles just as useful as the filters on a forced air furnace. These filter on the car need to be changed–if they are doing theie job, they get dirty.

I believe, today, that ALL car manufacturers use a ventilation system that maintains positive cabin pressure. The PRIMARY reason for this is to prevent exhaust gasses from ever getting into the vehicle, but it keeps dust and dirt out also. GM came out with a system in the '70’s called “Astro-Ventilation” where there was no “off” position for the heater blower. Even with the heater or A/C turned off, the fan still ran at low speed, slightly pressurizing the cabin with outside air…Many cars use this same system today…

This brings up an interesting point. Many owner’s manuals warn you not to run the heat on “recirculate” mode because humidity can build up, fog the windows, and lead to mold growth. “Recirculate” mode is really only for the air conditioner.

marky787, if you wife runs the heat in “recirculate” mode, she might make things worse for herself.

You are right about today’s cars. I remember the “Astro-Ventilation” system of GM. My 1978 Oldsmobile has this feature. Nash was the first to bring in and heat outside air. This feature was introduced in the late 1930’s. I think that many cars had a variation of this system as optional equipment when production temporarily ceased in 1942. I do remember cars where the heater was just a box under the dashboard and even this was an option. On many cars, a person paid even more for an upgrade to a fresh air heating system. My parents had cars where the heater was a box under the dashboard that just reheated the air in the car and recirculated the air. One car was a 1939 Chevrolet, one was a 1947 Dodge and the other was a 1947 DeSoto. In the warmer months, a valve under the hood was closed to prevent coolant from circulating through the heater. In the cooler months, the valve was opened. The fresh air heating system introduced by Nash compared with the old recirculating heater box is like comparing a forced air furnace with a coal stove. The last car that I remember having the recirculating box heater was the 1958 Studebaker Scotsman.

After reading this for a second time, along with the other comments. I wonder of there could be a leak in the system due to a loose clamp or maybe a torn hose? That could be admitting air from the engine compartment. Remember to check for leaks from your own car, exhaust etc. Sometimes it finds just a tiny hole and the gases go in there.

HEPA filters are great for particles, but a lot of the pollutants marky787 mentioned are gases. HEPA filters won’t stop them, though they may slow them down for a short while. And once the gas is trapped in the filter paper, it will pass through anyway. Some odors are small particles and the HEPA will stop many of them.

Since you need to bring in some air from the outside what could be the answer…Hmmmm. lets restrict the intake of outside air when that air contains items we don’t want. Great idea, trouble is I did not think of it. Since the late 90"s BMW (aren’t they always first with this stuff?) has had a system that will momentairly stop intake of all outside air (like when you are behind a diesel bus)So go BMW and leave the runaway cars to folks of “lesser” means.

BMW repair shops are booked up months in advance…Most of the mechanics are graduates of Santa’s toy shop…

If your wife is that bad…then recirculating air is only part of the solution.

Almost every car these days come with a cabin air-filter. Some are better then others. My wifes Lexus I can get two different filters. One just a standard filter or I can get a Charcoal filter that is great for allergies. My 4runner only has the paper filter option. Since we don’t have allergies it’s not a problem.