The Morongo Band of Mission Indians Quality Monitoring Project was funded through the California Air Resources Board Community Air Monitoring Grant Program (AB 617). The objective of the project is to place air monitors in various locations around the Morongo Reservation to measure and report air quality data in real-time.

This air monitoring network uses sensors that continuously detect airborne particulate matter equal to or less than 10 micrometers in diameter (PM10), particulate matter equal to or less than 2.5 micrometers in diameter (PM2.5), nitrogen dioxides (NO2), and ozone (O3).  These pollutants are considered “criteria air pollutants” and are regulated by the US Environmental Protection Agency under the Clean Air Act. This air monitoring network also detects the presence of volatile organic compounds (VOCs). In addition to these ambient air quality pollutants, the monitors also measure relative humidity, barometric pressure, and temperature.

Data from the air monitors is used to calculate Air Quality Index (AQI) values on the data page to provide context to the public on potential air pollution levels and how it relates to health risks. The AQI can be used by the public to reduce their exposure to potentially harmful levels of air pollution.

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Air Quality Index Details

The Air Quality Index (AQI) (formerly known as the Pollutant Standards Index) was issued on July 23, 1999 by the U.S. EPA for daily air quality reporting to the public. The index is designed to provide accurate, timely and easily understandable information about daily levels of air pollution and ranges from 0 to 500. The higher the AQI value, the greater the level of air pollution and the greater the health concern. An AQI value of 100 generally corresponds to the national air quality standard for the pollutant, which is the level EPA has set to protect public health. The AQI reflects revisions to the primary health-based national ambient air quality standards for ground-level ozone and particulate matter issued by U.S. EPA in 1997.

The intervals, color code assignment, and the terms describing the AQI are as follows:

AQI Index Values Levels of Concern Description of Air Quality
0 to 50GoodAir quality is satisfactory, and air pollution poses little or no risk.
51 to 100ModerateAir quality is acceptable. However, there may be a risk for some people, particularly those who are unusually sensitive to air pollution.
101 to 150Unhealthy for
Sensitive Groups
Members of sensitive groups may experience health effects. The general public is less likely to be affected.
151 to 200UnhealthySome members of the general public may experience health effects; members of sensitive groups may experience more serious health effects.
201 to 300Very UnhealthyHealth alert: The risk of health effects is increased for everyone.
301 and higherHazardousHealth warning of emergency conditions: everyone is more likely to be affected.

For more detailed information about the AQI, please visit the U.S. EPA’s AirNow website:


The data presented on this website includes ambient outdoor levels of ozone (O3), nitrogen dioxide (NO2), two sizes of fine particulate matter (PM2.5 and PM10), and volatile organic compounds (VOCs). Pollutants are continuously monitored, and results are updated every 60 seconds — refresh your browser to get the latest results.

Gases are measured using passive chemical electrode sensors that output voltages in response to changing levels of pollutants in the air. Algorithms are used to convert these voltages into concentrations of O3 and NO2.

Due to the sensitivity of sensors utilized in the air quality monitoring units, changes in temperature and humidity can impact pollutant concentration levels. Data reported during storm events may not be as reliable as during mild weather conditions.

Sensor Calibration

O3, NO2, PM2.5, and PM10 sensors used in the air monitoring network are routinely calibrated. State and regional operated sensors in Southern California are used to calibrate these sensors through collocation, where the air quality monitoring units are placed next to state and regional operated monitoring stations for a minimum of two weeks. After collocating, sensor data is compared, and calibration coefficients are applied if necessary, to improve data quality of the monitoring network

Particulate Matter (PM2.5 & PM10)

Particulate matter concentrations are measured as PM2.5 and PM10. PM2.5 are airborne particles with diameters of 2.5 micrometers or smaller and PM10 are particles equal to or smaller than 10 micrometers in diameter. Concentrations are measured in micrograms per cubic meter (µg/m3) using an Alphasense OPC-N3 particulate counter. In a field evaluation performed by South Coast Air Quality Management District (SCAQMD), the Alphasense OPC-N2 showed “overall good correlation with substantially more expensive instruments (GRIMM and BAM; EPA-approved FEM methods)”. A summary of the SCAQMD report can be found here, and the full SCAQMD field evaluation can be found here.

Particulate matter is generated by fossil fuel combustion in motor vehicles, agricultural burning, construction, and oilfield operations. Exposure to these particulates at elevated levels can result in increased risk of cardiovascular and respiratory illnesses, including cardiopulmonary and lung cancer. Certain populations, including children, pregnant women, the elderly, and those suffering from asthma or bronchitis are especially vulnerable to health conditions resulting from inhaling these fine particulates.

Ozone (O3)

Ozone (O3) is a highly reactive gas and concentrations are measured in parts per billion (ppb). Ground level ozone is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOCs) in the presence of sunlight. For this reason, ozone concentrations are typically highest in the afternoon during summer days with longer more intense daylight hours. Emissions from oil refineries, motor vehicles exhaust, gasoline vapors, and chemical solvents are some of the major sources of NOx and VOC (USEPA). According to the US EPA, exposure to unhealthy ozone levels can result in difficulty breathing, increased asthma attacks, higher susceptibility to lung infection, and respiratory illnesses, including chronic obstructive pulmonary disease (COPD).

Nitrogen Dioxide (NO2)

Nitrogen Dioxide (NO2) concentrations are measured in parts per billion (ppb). NOlevels are often highest during the nighttime because during the day NOreacts with sunlight in a chemical process that forms ozone (O3). Emissions from vehicles, construction, agricultural, and industrial operations are major sources of NO2. Harmful health effects from exposure to high levels of NOinclude respiratory illnesses and infections, most notably in sensitive populations including children and the elderly.

Volatile Organic Compounds (VOCs)

Volatile Organic Compounds (VOCs) are a class of gases that contain hundreds of compounds. These compounds react with nitrogen oxides in the atmosphere to form ozone. Measurements provided by the VOC sensors are given in millivolts (mV) and indicate the presence of a portion of the group of compounds that are considered VOC’s. Due to the capacity of the VOC sensor, these measurements provide only a general representation of the presence of VOC’s. A concentration can be determined if a specific VOC being measured is known. Sources of VOCs include emissions from motor vehicles, refineries, and other industrial operations. Some VOCs may cause short- and long-term adverse health effects, such as cancer and damage to the liver, kidney, and the central nervous system.