What do the air quality sensors measure and what don’t they measure?
The Los Angeles Unified Know Your Air Network includes more than 230 Clarity air sensors that measure fine particulate matter (PM2.5) — tiny particles in the air that can come from wildfire smoke, vehicle exhaust, and industrial pollution. These particles are 2.5 microns or smaller and can affect breathing and overall health.
As part of the launch of the “Know Your Air Network 2.0,” Los Angeles Unified has added new sensor modules at selected schools to measure additional pollutants, including:
• Coarse particulate matter (PM10): These are larger particles like dust, ash, and debris — especially important after wildfires or during construction activities.
• Nitrogen dioxide (NO₂): A gas linked to diesel truck and traffic emissions, which can also impact air quality near schools.
• Weather conditions: Wind speed and direction, temperature, and humidity are now being measured at select sites to help understand how pollution moves around campuses.
While the expanded sensors provide a more complete picture of air quality, they do not measure greenhouse gases (like carbon dioxide), ozone (smog), or certain industrial chemicals known as toxic air contaminants which all pose their own health and environmental risks.
What are the health problems associated with PM2.5 exposure?
Researchers have found prolonged exposure to PM2.5 air pollution to be associated with a variety of adverse health impacts including aggravated asthma, decreased lung function, irritation of the airways, coughing, difficulty breathing, irregular heartbeat, heart attacks, and premature death for people with heart or lung disease.
Will a short-term spike in PM2.5 cause health problems?
Monitoring data can show short-term spikes of PM2.5 of a few minutes. Health-based PM2.5 air quality exposure standards consider exposure rates averaged over one hour to one year. Regulators have not established health-based standards for exposure periods of less than one hour, which is one of the reasons why AQI is only reported as hourly averages. Those with pre-existing health conditions, the very young, and the elderly tend to be most vulnerable to the adverse health impacts of exposure to PM2.5. Air quality can change slowly or rapidly depending upon the weather, wind direction, time of day, inversion layer conditions, and other factors. Given the variability in air quality conditions, it is important to be aware but also prudent in how to respond in different situations. In general, it is important to minimize exposure to PM2.5 air pollution at all times, however, it is most important to take precautionary measures when PM2.5 levels are especially high and air quality regulators, such as the South Coast Air Quality Management District, have issued alerts.
What should I do if I see high readings?
If you notice high readings of the Air Quality Index (AQI), please refer to the AQI guide included in this information package. Also refer to OEHS’s Reference Guide 886.4, Air Quality, Weather, and Wildfire Advisory Procedures. Note that, in response to high levels of air pollution, principals have the authority to restrict outdoor activities, but only the superintendent has the authority to close a school.
