Particulate Matter

Maui Wildfire Data: Air

Particulate Matter in Lahaina

PM₁₀

PM_2.5

Click here to download the complete set of 1-hour PM₁₀ air monitoring data.

Click here to download the complete set of 24-hour PM₁₀ air monitoring data.

Ash that is in the air is in particles of different sizes. Since the beginning of debris removal operations on January 13, 2024, DOH has continuously measured the amounts of particles in Lahaina’s air. These measurements of “particulate matter” (or PM) are indicators of airborne ash and dust. PM is of health concern because it is small enough to enter people’s lungs.

DOH measures two different sizes of particles: PM₁₀ and PM_2.5. Measurements of these particles to date have consistently been below levels that are protective of public health.

PM₁₀ Findings

PM₁₀ are airborne particles that are smaller than fine grains of sand—and smaller than the thickness of human hair. PM₁₀ comes from many different sources, like wind-blown dust, construction, cars, and agriculture. PM₁₀ measured in Lahaina could contain ash from the fires, as well as dust and particles from other sources. Since January 13, 2024, DOH has collected daily PM₁₀ samples at the Lahaina Intermediate School, the Lahaina Boys & Girls Club, the Leialii Hawaiian Homelands, and one of the Lahaina wastewater pump stations.

Health Findings

Every daily PM₁₀ sample that DOH has collected to date at its four community monitoring stations in Lahaina has been well below levels that are protective of public health. This finding also applies to all PM₁₀ samples that the U.S. Army Corps of Engineers (USACE) has collected at debris removal sites and at the Temporary Debris Storage Site over the same time frame (click here to access the USACE data files).

DOH’s air quality monitoring in Lahaina shows that airborne PM₁₀ levels change from hour to hour. In more than 99.5% of the hourly samples, the measured PM₁₀ levels were below levels of health concern. On rare occasions (less than 0.5% of the time), the amounts of hourly PM₁₀ reached levels that might be of concern if they lasted for 24 hours—but they never did.

What is being done to reduce exposures to airborne particles

Many steps are being taken to make sure no one is exposed to unhealthy levels of PM₁₀. Soiltac® has been sprayed on the ash to keep it in place, and debris removal and TDS Site operations use various strategies—like water sprays—to control dust and keep ash out of the air. DOH will continue to collect daily air samples of PM₁₀ at four locations in Lahaina and will post advisories to this website if potentially unhealthy levels occur.

Chart of 24-Hour PM10 concentrations at community monitoring sites.

Bar Chart showing the low amount of hourly PM10 concentrations in Lahaina.

PM_2.5 Findings

PM_2.5 are airborne particles that are so small that they can go deep into your lungs. PM_2.5 in Lahaina could contain ash from the fires, and it could also come from other sources. DOH started its PM_2.5 air quality monitoring in Lahaina in January 2024, which was before debris removal operations began. DOH has continuously measured PM_2.5 at 50 locations throughout Lahaina since then. USACE also monitors for PM_2.5 at debris removal locations and at the Temporary Debris Storage Site.

You can access the last week of PM_2.5 air monitoring data in Lahaina from https://fire.airnow.gov. The next version of this website will include an option for downloading the entire history of these monitoring data.

Health Findings

Check https://fire.airnow.gov to learn about the current air quality throughout the Lahaina area. DOH’s Maui Wildfires Air Quality Guide for Particle Pollution fact sheet explains what the color-coded air quality indicators on that website mean for your health.

Note that the real-time data on the https://fire.airnow.gov website are preliminary and unofficial. The data await review and validation by qualified staff. The data may be revised or invalidated after review. DOH makes every effort to assert the validity and integrity of the data, but data can be affected by equipment malfunctions, technical difficulties, and other unforeseen circumstances.

Click here to access the USACE PM_2.5 monitoring data at debris removal locations and at the Temporary Debris Storage Site, for which all measurements to date are below levels of health concern.

Recommendation to residents

Continue to protect yourself from PM_2.5 and other harmful substances in ash. You can get real-time information on PM_2.5 levels in Lahaina and instructions for avoiding unhealthy exposures from https://fire.airnow.gov. If you do not have access to that website, take caution if you are in a location where there is visible dust or if the ash will be disturbed. To limit the amount of PM_2.5 you might breathe in, you can either temporarily leave the area or wear a snug-fitting dust mask or N95 mask—look for the words “NIOSH Approved” printed on the mask. Read more about how to protect yourself in DOH’s Maui Wildfires Air Quality Guide for Particle Pollution fact sheet.

What is being done to reduce to exposures airborne particles

Many steps are being taken to make sure no one is exposed to unhealthy levels of PM_2.5. Soiltac® has been sprayed on the ash to keep it in place, and debris removal and TDS Site operations use various strategies—like water sprays—to control dust and keep ash out of the air. So long as debris removal occurs, DOH will continue to measure PM_2.5 throughout Lahaina and will post advisories to this website if potentially unhealthy levels occur.