Calibration factors of SidePak AM520 and PurpleAir monitors for tobacco and marijuana aerosols.

This study addresses a practical but often-overlooked challenge: accurately measuring the fine particle pollution (PM2.5) produced by smoking and vaping tobacco and marijuana. Researchers conducted 24 controlled experiments in a residential room using two types of optical air quality monitors (SidePak AM520 and PurpleAir Zen) alongside gold-standard gravimetric filters to determine "calibration factors" - essentially correction factors that make these consumer-grade monitors more accurate. They tested multiple marijuana consumption methods including sativa joints, indica joints, and vape devices, as well as tobacco cigarettes, cigars, and vapes at varying source levels. The key finding: optical monitors significantly underestimate actual PM2.5 levels without proper calibration, with errors ranging from 4% to 16% depending on the device.

The research reveals important differences in how these monitors respond to different smoke types. SidePak AM520 calibration factors for tobacco and marijuana smoking were nearly identical (0.13-0.14), but marijuana vape produced a higher factor of 0.17. PurpleAir monitors showed the same trend but with substantially larger values (0.41-0.51), meaning they need bigger corrections. Notably, SidePak AM520 was more accurate after calibration (4% error) compared to PurpleAir (16% error), making it the better choice for consumers or researchers concerned about indoor air quality from cannabis use. The researchers also discovered marked differences between SidePak model versions, highlighting that device-specific calibration is critical—a finding with important implications for anyone relying on these monitors for health protection.

This work has practical significance for cannabis users, apartment dwellers in jurisdictions where smoking is permitted, and researchers studying indoor air quality. Accurate PM2.5 measurement is crucial because fine particles penetrate deep into the lungs and can affect not only the smoker but also secondhand smoke exposure to household members. Understanding that optical monitors underestimate exposure without proper calibration could lead to false reassurance about indoor air quality and represents an important step toward more reliable health monitoring tools.