Objective: To measure the ozone, carbon monoxide, and ozone produced by different cars. Background

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Lab: Measuring Air Pollution Using Gastec (From: Car Exhaust Analysis, Gastec Corporation, 2011)

(28 pts)




To measure the ozone, carbon monoxide, and ozone produced by different cars.


The Clean Air Act defines EPA’s role in monitoring and protecting the nation’s air quality and the stratospheric ozone layer. Since its passage 40 years ago, EPA has been required to set standards for air pollutants and to permit discharges into the air. The EPA sets National Ambient Air Quality Standards for six pollutants, called the criteria pollutants. These are: ozone, particulate matter, carbon monoxide, nitrogen oxides, sulfur dioxide, and lead. Due to concerns about climate change, the Supreme Court determined in 2007 that EPA should regulate carbon dioxide emissions. EPA has recently begun to regulate carbon dioxide. In this lab, we will measure concentrations of three of these gases: ozone, carbon monoxide, and carbon dioxide.

Ozone, O3, is “good up high, bad nearby”. Stratospheric ozone is responsible for protecting us from UV A and UVB radiation, which can cause sunburn, skin cancer, cataracts, immune system damage, plant damage, and phytoplankton damage. It can be depleted by gases like CFC’s (formerly in spray cans and refrigerants), halons (fire retardants), N2O (fertilizers), HCFC’s (replacements for CFC’s used as propellants and refrigerants), carbon tetrachloride (cleaners), and methyl bromide (pesticides). The Montreal Protocol (1987) phased out CFC’s and is currently being employed to phase-out of HCFC’s. The ozone that we will measure is tropospheric ozone, or “bad” ozone. This is formed by the reaction:

NOx + VOC’s + sunlight → O3 + other smog ingredients like PAN’s

Tropospheric ozone is a secondary pollutant, formed from other chemicals and sunlight in the atmosphere. It is a strong oxidant. In humans, it causes coughing, chest pain, throat irritation, and congestion. It can irritate asthma, emphysema, and bronchitis. When 0.1 ppm of ozone is inhaled for two hours, the lung capacity can decrease by 20%. When 1 ppm is inhaled for six hours, it causes headaches or bronchitis. When rats were exposed to 10 ppm, they suffered pulmonary edema and died, indicating that ozone is quite toxic.

Carbon monoxide, CO, is a colorless, odorless, highly toxic gas produced by incomplete combustion of carbon-containing materials. It is given off by industrial burning, some stoves, cigarette smoke, and motor vehicles. Carbon monoxide interferes with the hemoglobin’s oxygen-carrying ability, so cells become deprived of oxygen. Symptoms of carbon monoxide poisoning include headache, dizziness, loss of judgment, nausea, heart problems, and potentially death.

Carbon dioxide, CO2, is a carbon-cycle gas naturally present in the atmosphere is small concentrations. It is naturally added to the atmosphere by aerobic respiration, volcanic activity, hot springs, geysers, and dissolving carbonate rock. It is removed from the atmosphere by photosynthesis and by ocean organisms like coral, some algae, and mollusks. The chief anthropogenic source of carbon dioxide is burning fossil fuels. Environmental scientists have been concerned because carbon dioxide has been increasing at an increased rate since the industrial revolution. Since carbon dioxide is a powerful greenhouse gas, it has caused the average temperature of the earth to warm and has been linked to ocean acidification. Under a Supreme Court ruling in 2007, EPA has begun to regulate carbon dioxide under the clean air act.

  • Gastec sampling tube

  • Carbon dioxide tubes 2EH

  • Carbon monoxide tubes 1EL

  • Ozone tubes 18EL

  • Nitrogen Oxide Tube 11 EL

  • Old newspaper

  • Plastic garbage bags (~10 gal)

  • Sharpie

  • Rubber band or twist tie

  • Tape (1 poll)

  • Scissors (1 pr)

  • Automobiles to test


Before starting, propose a hypothesis as to what differences you might expect to see. (2 pts)

1. Prepare the plastic bag for collecting the samples:

a. Cut a 2-3 mm hole toward the bottom on the bag. Using a marker, make a circle around the hole so you can find it when you need it.

b. Place a small piece of tape over the hole and make sure it is secure. Fold the end of the tape on itself to create a small tab. (This will make it easier to pull back each time you perform a test on your sample.

2. Prepare the pump to collect samples:

a. Make sure the pump handle is pushed into the chamber.

b. Break off the tip of both ends of the carbon dioxide tube and place a pink rubber tip on the end marked “G”.

c. Place the other end of the tube securely in the yellow Gastec pump with the arrow pointing toward you.

3. Collect the exhaust sample:

a. Wrap the outside of the tailpipe with newspaper without blocking the exhaust.

b. Compress the bag to remove all the air from it and make sure the sampling hole is secure before collecting the sample.

c. Hold the plastic bag around the newspaper that is wrapped around the tailpipe.

d. Have someone start the car while another person is ready to collect the sample of exhaust and twist the bag closed once it fills with car exhaust. (This happens very quickly so review steps before performing the test.)

e. Secure the rubber band or twist tie around the top of the bag so you are able to test the sample for three different gases carbon monoxide, carbon dioxide, and ozone.

4. Test the Sample: Carefully pull back the tape covering the sampling hole and insert the carbon dioxide tube tester into the bag and pull the pump handle until you hear a click. Wait for 1 minute, keeping the tube in the bag for at least one minute. (See the diagrams on the measurement sheet for details.)

5. Collect the data: Write down the data on the table, indicating the number associated with the color change. This represents the % of the particular gas.

6. Repeat Steps 1-5 for carbon monoxide, nitrogen oxide, and ozone gases.

7. Leave the car running 5 minutes. Using a different bag, repeat steps 1-5 for all three gases. CAUTION: The tailpipe can get hot after running 5 minutes. DO NOT TOUCH THE TAILPIPE WITH YOUR BARE HANDS AND DO NOT BREATHE THE FUMES FROM THE AUTOMOBILE.

Below are the results collected in the experiments: (12 pts)

Car 1:

Car 2:

Car 3:



5 minutes


5 minutes


5 minutes

Carbon dioxide

Carbon monoxide


Nitrogen Oxide

Make a graph of the data. (5 pts)


1. Which target gas was highest at start up? (1 pt)______________________________

2. Which target gas was highest after 5 minutes?(1 pt) _______________________________

3. Was there any difference between the two vehicles tested? If so, what was the difference? (2 pts)

4. Which target gas showed the greatest change over 5 minutes? (1 pt) ________________________

Propose a hypothesis as to why this might be true. (1 pt)

5. What scientific, or social, or technological concerns or opportunities could/should be addressed based on your findings? (1 pt)
6. Was your hypothesis met? Explain. (1 pt)

7. What experiment would you want to try next? (1 pt)

8. Would you expect to find large amounts of tropospheric ozone in your sample? Why or why not?

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