Particulate Matter

Maui Wildfire Data: Air

Particulate Matter in Lahaina

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.

Community air monitoring took place in late 2023, 2024, and early 2025. Monitoring was completed February 19, 2025. Data are available below.

Ash that is in the air is in particles of different sizes. Since the beginning of debris removal operations on January 13, 2024, through the completion of debris removal in spring 2025, DOH 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 measured two different sizes of particles: PM₁₀ and PM_2.5. Measurements of these particles have consistently been below levels that are protective of public health.

PM₁₀ Findings

PM₁₀ particles are airborne particles that are smaller than fine grains of sand—and they are 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 and dust and particles from other sources. The locations where DOH monitored air quality changed over time. Initial locations monitored for daily PM₁₀ samples from January through August, 2024, were:

Lahaina Intermediate School
Lahaina Boys & Girls Club
Leialii Hawaiian Homelands
Lahaina wastewater pump station #4

Later, DOH relocated stations to more accurately monitor the active work area. Changes to DOH air monitoring locations were as follows:

On August 23, 2024, DOH relocated the Leialii Hawaiian Homelands station to Opukea Townhomes.
On August 24, 2024, DOH relocated the Lahaina Boys & Girls Club station to Lahaina Skate Park.
On December 20, 2024, DOH relocated the monitor at the Lahaina Recreation Center due to activity resuming at the Center’s baseball field. This monitor was relocated to Lahaina Pump Station #6.
On January 18, 2025, DOH relocated the monitor at the Lahaina Intermediate School to the Maria Lanakila Catholic Church.

Airborne PM₁₀ levels at the monitoring stations changed from hour to hour, and 24-hour average (or daily) levels were compared to EPA’s health-based air quality standard for PM₁₀: 150 micrograms per cubic meter (µg/m³). DOH monitored these levels to ensure that concentrations of airborne particulate matter did not exceed safe levels for public health.

Health Findings

With few exceptions, every daily PM₁₀ sample collected in Lahaina has been below levels that are protective of public health. The exceptions were for the daily PM₁₀ samples collected at the following dates and locations:

May 15, 2024, at the Lahaina Intermediate School
August 24–28, 2024, at the Lahaina Skate Park
August 25, 2024, at the Lahaina Intermediate School
September 9–13, 2024, at the Lahaina Skate Park
January 6, 2025, at the Lahaina Intermediate School and Pump Station #6
January 17, 2025, at the Lahaina Intermediate School and Pump Station #6
January 26, 2025, at Pump Station #6
January 27, 2025, at Pump Station #6 and the Maria Lanakila Catholic Church
January 30–31, 2025, at Pump Station #6 and the Maria Lanakila Catholic Church

For these exceptions, no debris removal crews were working in the area during sampling times, and visible dust was not observed. These elevated levels are therefore not believed to be the result of debris removal. The elevated levels may have been related to the proximity of the highway for the Skate Park location and related to high humidity and volcanic smog for the January 2025 measurements.

PM₁₀ samples that the U.S. Army Corps of Engineers (USACE) and its contractors have collected at debris removal sites and at the TDS Site over the same time frame have also been below levels of health concern (click here to access the USACE data files). The data collected at these worksites have been consistently below levels that would pose unacceptable risks for workers.

What is being done to reduce exposures to airborne particles

Many steps have been 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 monitor air quality during the transfer of debris from the TDS Site to the PDS and will post advisories to the TDS/PDS page if potentially unhealthy levels occur.

PM_2.5 Findings

PM_2.5 particles 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 continuously measured PM_2.5 at multiple locations throughout Lahaina in 2024 and early 2025. USACE also monitors for PM_2.5 at debris removal locations and at the TDS Site.

You can view current conditions using Fire and Smoke Map, which provides Air Quality Index (AQI) advisory levels for PM_2.5.

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 map above 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.

You can access the USACE PM_2.5 monitoring data for debris removal locations and the Temporary Debris Storage Site. All measurements to date at these locations have been below levels of health concern for workers.

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 DOH’s Ambient Air Quality Data website and further instructions for avoiding unhealthy exposures from https://fire.airnow.gov/. If you do not have access to these websites, 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 have been 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. DOH will continue to measure PM_2.5 and PM₁₀during transfer of debris from the TDS Site to the PDS and will post advisories to the TDS/PDS page if potentially unhealthy levels occur.