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Method to Measure CO2 concentration in room

  1. Aug 13, 2008 #1
    Hi all, i have been assigned to study indoor air quality and car cabin air quality project.

    My Problem is:

    How to measure Carbon Dioxide concentration in that constant volume of air? (consider there will be changes in the concentration and i need to quantify or contrast it at least.)

    Yes i know there are multiple gas sensors out in the market, but those are quite beyond the allocation available for this project.

    i have heard of but have not tried using chemical solution such as (liquid calcium carbonate) actually can measure the differences of the CO2 concentration?

    Thanks in advance.
     
  2. jcsd
  3. Aug 13, 2008 #2

    russ_watters

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    Staff: Mentor

  4. Aug 13, 2008 #3
    unfortunately yes :( this is a high school project that im working on, so we are not expected to exceed $200 total budget if possible.
     
  5. Aug 13, 2008 #4
    Carbon DIOXIDE? You're talking about trying to measure the deviations from a relatively low (but already prevalent) component of our atmosphere (around 1 part volume per 2500 if I recall). Have you researched the implications of increased/reduced carbon dioxide on the "quality" of air? How do you define "quality" of air? Are you prepared to defend your project based on the properties of carbon dioxide?

    I think you might be confusing the idea with carbon monoxide. As far as I know, deviations in carbon dioxide should not be that dangerous (or even uncomfortable depending on how small) to humans. If you've ever tried to breath in the vicinity of evaporating dry ice, you'll get a feel for what I mean. The vapor coming off of dry ice is the carbon dioxide, and the percentage by volume SKYROCKETS, leaving you starved for oxygen and retreating to a more ventilated area. Carbon *monoxide* however, bonds to your blood in significant enough levels and impedes your body's ability to carry oxygen, causing an induced "suffocation" of sorts that tires you out and puts you to sleep. Happened to one of my neighbors down the road not too long ago--furnace problems. Thankfully one of them realized it and everyone came out alright.

    Regardless, the most effective way I can think of pulling what you're suggesting (without some sort of chemical reaction or fancy detector) off is by creating airtight balloons of the samples in question, and then using balances to determine differences in composition by relating back to the change of distribution of gasses. You would be taking measurements on an order of magnitude well beyond the common household scale, and would have to tackle a ton of variables like making sure the balloons were precisely the same, comparing the pressures of the balloons, etc..

    Actually, along those lines you could potentially set up a device measuring rates of effusion through a medium based on the differences in molecular sizes, but even with an effusion based approach you would be looking at ridiculously difficult comparisons for a highschool level of equipment.

    Best of luck with your project. :)
     
  6. Aug 13, 2008 #5

    russ_watters

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    Cvan, carbon dioxide is, in fact, used as a benchmark for indoor air quality measurements. AC systems that vary their ventilation rate do so based on indoor vs outdoor CO2 levels.
     
  7. Aug 13, 2008 #6
    Ahh, thanks russ. I won't pretend that I've got any knowledge on the topic, it just seemed like a more likely candidate for air quality without any background on the subject.
    Regardless--do you happen to know how they differentiate between the indoor and outdoor levels?
     
  8. Aug 13, 2008 #7

    russ_watters

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    With indoor and outdoor sensors and a controller that subtracts one from the other.

    I once did a study on a school that didn't have any ventilation (in violation of code) and the CO2 levels inside were 1500-3000 ppm inside vs 450-550 outside.
     
  9. Aug 13, 2008 #8

    russ_watters

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    Astra, you might try playing the 'I'm a poor high school student' card with a local engineering company and they may be able to let you borrow a sensor or otherwise help you with your report. Google for "hvac engineer" and your location.
     
  10. Aug 18, 2008 #9
    Or take a sample and bring it to a local University's chemistry department maybe they'll send it through a gas chromatograph for you . Make sure to name it: "Integrated research experience for high school students".
     
  11. Aug 21, 2008 #10
    ASHRAE recommends indoor CO2 levels not to exceed 700 PPM greater than outdoor levels.

    You can purchase a SenseLife air quality monitor for $180. it measures CO2, temperature and humidity.

    CO2 range is 0-9,999 PPm +/- 50 PPM

    www.CO2meter.com
     
  12. Aug 21, 2008 #11
    I'm not sure how helpful this will be, but you could try to run a bubbler through a vial with a pH indicator in it. The carbonic acid produced could give indication of the CO2 in the air. Might not be sensitive enough though. Just a suggestion.
     
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