Absorbent filter tape is used for Beta Attenuation Monitors or BAM for short; BAM is how we measure PM.25 content in the air. PM 2.5 is a category of organic compounds small enough to enter the lungs and cause both short-term and long-term harmful effects. Filter tape traps particles over a set time for the monitors to measure air quality. Those values are used to calculate the Air Quality Index which is a system used to report how clean or polluted the air is, and what health effects might be of concern.

Wind carries particulates far and wide. When people enter Yosemite, they breathe the air that is shared across mountains, cities, and nearby communities. There are no boundaries for the breeze; thus, consider the wind for there is no distance between the lungs and the sky above.