Through my work I got a CO2 detector, a cool little professional Dräger gadget. While in a taxi today, I measured CO2 concentrations from 4-7,000 ppm (0.4-0.7%). I got a similar result when driving my own car with only one passenger.

Like everybody else, I also use the air "recycle" function to maximize the aircon output. Modern cars are fairly air-tight, so CO2 concentrations build up pretty quick.

Same thing often happen in planes, hence why most people feel sleepy when flying.

A little trivial about CO2:

450 ppm: Normal clean air

5,000 ppm: OSHA max exposure for an 8 hour work day

30,000 ppm: 15 min max short time exposure

40,000 ppm: Exhaled air when breathing normal

90,000 ppm: Lethal at 10 min

10,000 ppm = 1%

And you needed some fancy gadget to figure this out...

That's why it's important to open the window a crack or let in outside air from the air-con for a few minutes every hour if on a long trip. Do the same (window trick) when in a taxi from Bangkok to Pattaya too.

I think it's a little ab normal.

Thanks for posting!

That all sounds right - that's why every manufacturer provides a warning about using A/C recirculation.

What would be even more intresting would be to measure the CO2 levels with re-circ off or windows wide open, in a good old Sukhumvit or Petchburi Rd traffic jam

Thanks for posting!

That all sounds right - that's why every manufacturer provides a warning about using A/C recirculation.

What would be even more intresting would be to measure the CO2 levels with re-circ off or windows wide open, in a good old Sukhumvit or Petchburi Rd traffic jam

Street level CO2 concentrations was 0, or at least below 500 ppm, at noon today. I will take a few measurements during rush hours at Sukhumvit and in some of the underground clubs.

mostly I feel drowsy in cars when driving too slow. Happens on highways only. Switzerland, France.

I think a minimum 150 KmH is required to keep the driver active enough.

And I thought after working 10 - 12 hours then driving another 800 km after work was why I got tired with no sleep. Good to know . . .

mostly I feel drowsy in cars when driving too slow. Happens on highways only. Switzerland, France.

I think a minimum 150 KmH is required to keep the driver active enough.

yepp, 160 kmh and aircon on fresh air, I never feel sleepy :lol:

but honestly, aircon on recycle, the CO2 never gets vented on the occasions clean air is available

which I prefere in a taxi as a tranquilizer, but not while I am driving

It's not the CO2 that does the most harm it's the CO usually from the fact that they had a CNG or an LPG installation done and the holes made were not properly sealed so it leaks into the passenger compartment.

I've been to the track many times here where this is commonly overlooked and is quite dangerous and the reason for many track incidents and lapses of concentration and reaction time as CO builds up in the blood stream over time and accumulates unlike CO2..

Gaping holes in the cars body/bulkhead, floor, etc. and some in the back to let air pass through but what is not understood is that the back of the car has a low pressure area where the exhaust loops back and if you have holes back there it comes inside the car also through the firewall, shoddy at best.. But everyday drivers here are given just as little consideration whenever any work is done that requires going through the cars sealed bulkhead, it's just hidden behind the carpeting so one notices..

I'd suggest this is not that big an issue with taxi's since the doors are being opened constantly with new passengers..

And you needed some fancy gadget to figure this out...

Edit: Hmmm, not sure why this post came out all wrong. Lazy to type it all again!