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A vendor of VOC (Volatile Organic Compound) sensor claims the VOC concentration correlates highly to CO₂ concentration in a typical conference room:

Figure 2 illustrates the correlation of true CO₂ and concentration of mixed gases measured in a typical conference room.

Other VOC vendors also claim a cheap VOC sensor can be used as a reliable counterpart of a more expensive CO₂ to help decide when to ventilate in an office or a household, and quite a few of them recompute the measured VOC concentration to a "CO₂ equivalent level":

Clean Air Control - Swegon

When an occupant emits CO2, this creates a proportional amount of emissions/impurities which are measurable by the VOC sensor

Breath: Acetone, Ethanol, Isoprene

Example: 25% CAC output signal is equivalent to CO2 800 ppm

GAS & SPECIALTY SENSORS

The BA/BS3 VOC measures these VOCs and serves as an indicator of space occupancy with the same reliability as CO2 transmitters. VOC: 0 to 2,000 CO2 PPM equivalent

VOC Duct Sensor

The output of the BAPI Volatile Organic Compound (VOC) Sensor is 0 to 100% VOC contamination. The VOC contamination can be turned into a CO2 ppm equivalent by multiplying by 2,000

As the VOC vendor claim is obviously not independent, I would like to know what independent sources say about this?

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  • I think the claim is only likely to be true in specific sorts of room, specifically where the number of people correlate with the number of VOC sources (like new carpet, paint, new furniture etc.) And you shouldn't need a sensor to work out a building is badly ventilated.
    – matt_black
    Nov 14 '12 at 16:27
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    A CO2 sensor can be a great help to determine how much ventilation you need, which can be important energy saver during the heating season.
    – Suma
    Nov 14 '12 at 18:57
  • A factor causing correlation could be if human breath contains VOC as well. Does it, and how much? I have no idea on this.
    – Suma
    Nov 14 '12 at 18:58
  • Erm, what is VOC? A question about VOC should probably clarify this … Nov 15 '12 at 15:30
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    It's not that they correlate high Co2 with high VOCs; but that they correlate rising CO2 with rising VOCs. In an occupied room, both will rise quickly if the room is badly ventilated; and they will rise much more slowly, or stay flat, if it is well ventilated. But that's just basic physics, right?
    – 410 gone
    Nov 15 '12 at 15:42

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