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Air Quality Experiment: Indoor V. Outdoor

You can design a simple experiment to compare indoor and outdoor air quality by using your Kids Making Sense PM sensor. Begin by measuring air pollution inside of your house, then walk outside, and then back inside. What did you find? Is the air quality better or worse indoors? Can you explain your results?

We tried the experiment in two different locations exposed to wildfire smoke, with surprising results.

In Location 1, we found that air pollution levels were elevated inside the house, but not nearly as high as outside. Although the windows and doors had been kept shut to keep the smoke out, we did not have any type of air filtration system, such as an air conditioner or a portable air purifier.

We turned on the sensor and measured the particulate matter while standing inside by the front door. Then we opened the front door and walked outside (A) where it was quite smoky. We then came back inside (B) and closed the door.

Experiment 1 showed much higher pollution levels outdoors.

In Experiment 2, the PM concentrations inside were slightly elevated, but not very high. However, when we walked outside (C), PM concentrations decreased. That was not what we expected! We then walked back inside (D) and confirmed that the air outside was actually slightly cleaner than the air inside the home.

As with any scientific experiment, the value is in understanding why we got these results. Some indoor activities that may have caused higher PM levels indoors include cooking and dusting. Another possibility is that polluted air was trapped inside, while winds outside shifted and blew the smoke away.

Experiment 2 showed slightly lower pollution levels outdoors.

In both cases, we could improve our indoor air quality by using an air filter. These two examples highlight that the same experiment can often result in different outcomes - the value is in understanding why!

What will your students discover when they conduct their own experiments?