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Breaking the Mold
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Dust Busters to the Rescue | Unfolding the Mystery of Mold
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Indoor Air: What's the Matter?

Lesson Goals:

Students will develop a greater awareness of the variety and amount of particulate matter in the air. They will try to locate general sources of pollution for a specific area and develop some suggestions for improving air quality.

Curriculum Connections:


  • Knows that materials may be composed of parts that are too small to be seen without magnification
  • Establishes relationships based on evidence and logical argument (e.g., provides causes for effects)


  • Knows environmental and external factors that affect individual and community health

Environment and Society

  • Understands ways in which human-induced changes in the physical environment in one place can cause changes in other places (e.g., the effect of a factory's airborne emissions on air quality in communities located downwind)
  • Understands the environmental consequences of people changing the physical environment (e.g., the effects of tk on indoor air quality)

Video Tie-In:

Air Pollution documentary video clip

Glossary Terms:

biological contaminants, combustion, emissions, environmental tobacco smoke, mold, particulates, pollen, pollutant, pollution

Time Required:

Two 20-minute class periods


  • Microscopes or magnifying glass
  • Petri dishes
  • Petroleum jelly
  • Masking Tape
  • Graph Paper

Activity Overview:

According to the Environmental Protection Agency, indoor air pollution can be as much as 100 times higher than outdoor levels. Because most people spend at least 90 percent of their time indoors, indoor air quality is a growing concern. Most major air pollutants are invisible, but not all. In this activity, students will get a close-up look at some of the particulate matter present in their indoor environment.


  1. Ask students if they think the air in their classroom is clean. Determine if the class can see or smell anything in the air that might be polluting it. Then spend some time explaining that the air we breathe--both indoors and out--contains tiny microscopic particles, called particulates that consist of things such as dirt, soil dust, pollens, molds, ashes, and soot. Particulate pollution comes from such diverse sources as factory and utility smokestacks, vehicle emissions, wood burning, mining, construction activity, agriculture, and cigarette smoke. Biological contaminants such as mold, dust mites, and pollen can also be suspended in the air. Because particulate matter can be very small, it is easily breathed in and trapped in the lungs, causing various health problems.

  2. Explain to the class that they are going to conduct an experiment that will reveal what's in the air they breathe right there in the classroom.

  3. Instruct each student to coat the inside of a petri dish with petroleum jelly. Have students place the uncovered petri dishes in various locations around the classroom (near a window, next to a fan or ceiling vent, inside a closet or drawer, beside the pet hamster's cage, etc.). Make sure students put a masking tape label on their dishes marking the location each is placed. Put your own jelly sample near a candle that you will light for a few minutes every day. And put a lid on one of the coated petri dishes to serve as a control.

  4. After a week, or some other specified time period, have students examine the particulate matter collected on the petri dishes using either a microscope or a magnifying glass.

  5. Have students compare exposed petri dishes with the control and record their observations to the following questions:
    • What are the locations of the petri dishes that had the most particles?
    • What are the locations of the petri dishes that had the fewest particles?
    • Describe what the particulate matter on each dish looks like.
    • What is the likely source of the pollution on each dish?
    • How might this pollution be reduced?
    • Evaluate the air quality of your classroom. Based on your observations, write an article or letter to the editor of your school newspaper describing how you feel about the problem of indoor air pollution.

Follow Up Ideas:

  • Students can take a jelly coated dish home to test for particulate matter and then report their findings to the class.
  • Students can leave a sample collector outside for a week (sheltered from precipitation) and keep a journal of its progress each day and report to the class.

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