Preference: Charcoal or no?

[Johnson Johnson]

I don't understand why anyone would put charcoal in an air filter. Odours (for the most part) are simply complex organic chemicals. Sure charcoal absorbs odours, and (if so) it will be fully saturated in about 30 minutes. Then what?

If it's saturated it won't be able to absorb more odours. And if it releases odours later, what was the point? Do you want your car to smell vaguely of skunk for weeks, or for a few minutes and get it over with.

I suspect this is only an advertising gimmick. What am I missing?

Because it filters out NOX and other toxic gases.

 

[ecotourist]

Because it filters out NOX and other toxic gases.

Charcoal works fine at absorbing toxic substances. [We used to make people who had taken an overdose drink a bunch of charcoal and water.]

But how much capacity do you think a cabin filter has? Not very much. If there were toxic gases in your environment there might be enough capacity for a day, possibly a couple of days. And after that it can absorb no more, and might even slowly release those toxic gases. Unless you're prepared to replace your cabin filter every week or so, the charcoal in a cabin filter is pointless. I think it's an advertising gimmick.

 

[Jetronic]

Charcoal works fine at absorbing toxic substances. [We used to make people who had taken an overdose drink a bunch of charcoal and water.]

But how much capacity do you think a cabin filter has? Not very much. If there were toxic gases in your environment there might be enough capacity for a day, possibly a couple of days. And after that it can absorb no more, and might even slowly release those toxic gases. Unless you're prepared to replace your cabin filter every week or so, the charcoal in a cabin filter is pointless. I think it's an advertising gimmick.

the charcoal type filters are often of a stiffer construction, I've come across several collapsed regular cabin filters, never a charcoal one. Now, I realise the issue is mostly that the filter was left too long to begin with.

I haven't even checked the filter in the MG yet, I know it has a 2 year/20k miles service interval.

edit; so I went out and checked the filter, it's a micronair pf202. While it was out i removed some of the silver birch seeds it caught. and 1 tiny bird feather.

the filter seems like it has a charcoal filling, but extremely thin. it could just be dirt colouring the filter

 

[Johnson Johnson]

Charcoal works fine at absorbing toxic substances. [We used to make people who had taken an overdose drink a bunch of charcoal and water.]

But how much capacity do you think a cabin filter has? Not very much. If there were toxic gases in your environment there might be enough capacity for a day, possibly a couple of days. And after that it can absorb no more, and might even slowly release those toxic gases. Unless you're prepared to replace your cabin filter every week or so, the charcoal in a cabin filter is pointless. I think it's an advertising gimmick.

That's not how they work. The gas's are held in the charcoal, once the fan is switched off they dissipate through the vents in the scuttle. They're actually (depending on brand, use a good one) very effective.

 

[f355spider]

The Lexus is the only vehicle we own that has a cabin filter. I use OEM/Denso filters which are charcoal.

There's also an air sniffer attached to the radiator support that will switch the HVAC from outside to inside if it detects HC/CO in outside air. I've seen it switch over only once since 2008.

View attachment 140465

BMWs have had the smog sensor since the late 1990s I believe. I know my 2001 BMW 540 has it, but like you, I have rarely seen it activate. I was contemplating replacing the sensor, but noticed my newer 2018 BMW M550ix never switches over either...so it may be working as intended.

 

[Johnson Johnson]

BMWs have had the smog sensor since the late 1990s I believe. I know my 2001 BMW 540 has it, but like you, I have rarely seen it activate. I was contemplating replacing the sensor, but noticed my newer 2018 BMW M550ix never switches over either...so it may be working as intended.

What about particulate matter and NOX? I very much doubt a sensor from 2001 is picking up that much by today's standards TBH.