Measuring a high PM level may or may not be cause for concern. If your students measure a high PM level, have them make a note, including when and where the measurement was taken, how long it lasted, and what they observed happening in the area at the time. High readings that last only a short period of time may be caused by something happening close by, like smoke from a cigarette or kicked-up dust. Levels that are high for longer periods of time may be more concerning. In these cases, think about steps your students can take to bring the readings down, like moving to a different area or increasing ventilation (if they are indoors).