December, 2002, Earth Science Experiment:

Indoor CO2 Build-Up

- Purpose
- Background Information
- Equipment & Supplies
- Software & Probeware Set-up
- Experimental Procedure
- Data Analysis
- Conclusions and Extensions


PASPORT CO2 Gas Sensor
(PS-2110)

PASPORT CO2 Gas Sensor

ScienceWorkshop CO2 Gas Sensor
(CI-6561 - Available Jan 2003)

ScienceWorkshop CO2 Gas Sensor

CO2 graphic

Purpose:

Students will use a CO2 Gas Sensor to measure the amount of CO2 in a classroom. Measurements will be taken during a class period and students will observe the changing CO2 levels.

 

Background Information:

Carbon dioxide is a colorless, odorless, incombustible gas that is a product of respiration and combustion and a natural component of the air on this planet. It is one of several byproducts generated by automobiles and is believed to be a leading contributor to the so-called "greenhouse effect" linked to rising temperatures around the planet.

The amount of CO2 in a given air sample is commonly expressed as parts-per-million (ppm) -- the number of molecules of carbon dioxide per million molecules. The outdoor air in most locations contains about 400-450 ppm carbon dioxide. Higher outdoor CO2 concentrations can be found near vehicle traffic areas, industry and sources of combustion.

Where indoor concentrations are elevated (compared to the outside air) the source is usually the building's occupants. People exhale carbon dioxide -- the average adult's breath contains about 35,000 to 50,000 ppm of CO2 (100 times higher than outdoor air). Without adequate ventilation to dilute and remove the CO2 continuously generated by occupants, CO2 can accumulate. Students and educators can spend about half their waking hours at school. Therefore, maintaining adequate indoor air quality (IAQ) in buildings is becoming a top priority for school administrators.

Hypothesize: Will the CO2 levels in a classroom increase or decrease during a class period? Why?

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Equipment & Supplies:

For each lab group:

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Software & Probeware Set-up:

  1. Ensure that your USB Link, Xplorer or ScienceWorkshop 500 interface is connected to the computer.

  2. Click on one of the links below to download a pre-configured DataStudio file for this experiment, and then open the file.

    PASPORT users: PS Windows (.zip file) or PS Macintosh (.sit file)

    ScienceWorkshop 500 users: (DataStudio files will be available in January, 2003, when the CO2 Sensor is released.)

    When the file is opened, you should see a Graph Display of CO2 vs. Time, as well as a Digits Display of CO2.

  3. Connect the CO2 Sensor to the Xplorer or USB Link (PASPORT users) or plug the CO2 Sensor into channel A of the 500 Interface (ScienceWorkshop 500 users).

    If you are using the ScienceWorkshop 500 Interface, be sure the interface is turned on and the CO2 Sensor is associated correctly in the Experiment Setup window.

  4. The sample rate has been set to take a measurement once every 15 seconds. You can verify this by clicking the Setup button ( ).

  5. If you are not using the pre-configured DataStudio file, first click the Setup button ( ). The Sample Period default will read "5 Hz." Change it to "10 Seconds" by using the pull-down tab. Click ( ) to close the Experiment Setup window.

  6. Calibration of the CO2 Sensor is not required for most activities, as the sensor is factory calibrated. Over time, the sensor’s characteristics may change. To restore the sensor to its factory-calibrated state, calibrate in typical outside air conditions (approx. 400 to 450 ppm). For help with calibration procedures, refer to the sensor manual or Quick-Reference card or access DataStudio’s help menu.

  7. Resize and arrange the display as needed.

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Component
Symbol
Content
Nitrogen
N2
78.084% 99.998%
Oxygen
O2
20.947%
Argon
Ar
0.934%
Carbon Dioxide
CO2
0.033%
Neon
Ne
18.2 parts per million
Helium
He
5.2 parts per million
Krypton
Kr
1.1 parts per million
Sulfur dioxide
SO2
1.0 parts per million
Methane
CH4
2.0 parts per million
Hydrogen
H2
0.5 parts per million
Nitrous Oxide
N2O
0.5 parts per million
Xenon
Xe
0.09 parts per million
Ozone
O3
0.07 parts per million
Nitrogen dioxide
NO2
0.02 parts per million
Iodine
I2
0.01 parts per million
Carbon monoxide
CO
trace
Ammonia
NH3
trace

 

Experimental Procedure:

  1. Place the CO2 Gas Sensor in an open area in the classroom.

  2. Wait approximately 30 seconds to allow the CO2 reading to stabilize.

Data Collection & Recording:

  1. Click the Start button ( ) to begin collecting CO2 data.

  2. Be careful not to disturb the sensor during the experiment since sudden or excessive air movement, or CO2 from breathing, will influence the results.

  3. Click the Stop button ( ) to end the experiment near the end of the class period.

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Data Analysis:

  1. Scale the axes to fit the data using the Scale to Fit button ( ) in the Graph toolbar.

  2. Use the Note Tool ( ) to annotate where on the graph any observed variables -- i.e., heater or A/C turned on/off, door or windows were opened/closed.

  3. Examine the graph and study the data. At what point was the CO2 reading the highest? The lowest?

Conclusions and Extensions:

  1. How did the level of CO2 compare to your hypothesis or expectations?

  2. Explain why any difference occurred.

  3. How would a reading from the first class period in the morning compare to one at the end of the day? Why?

  4. As a comparison, if you’re using an Xplorer datalogger or ScienceWorkshop 500 interface, take the CO2 sensor outdoors and obtain a measurement of the outdoor air. Is it higher or lower than your indoor reading? Why?


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