3 ms·

My tests with my meter don't imply that is correct. Almost immediately on recirculate the PPM goes up and stays there.

• graeme 8y ago
  This is almost certainly correct. An unventilated space as small as a car will increase within 30-60 seconds, based on my testing of small indoor rooms.
  • jtms 8y ago
    Wow I wonder if anyone has done a study on any correlation between cabin CO2 levels and driver safety?