Photo courtesy of PurpleAir.
Since 2023, Emerald Keepers has been monitoring and publishing data on Coronado’s air quality. The information is gathered from four air-quality monitors Emerald Keepers installed around Coronado, which provide information on the local Air Quality Index (AQI).
An analysis of Coronado’s 2025 air quality from January through October shows 29% of days with unhealthy air at the Shores. The monitor at 1st Street shows 20% of the days with unhealthy air, and the Coronado Cays monitor reported 14% of days unhealthy.
MORE MONITORS NEEDED
To better understand air-quality trends, Emerald Keepers is looking for up to four additional homeowners to host an air-quality monitor on their property. Neighborhoods with the greatest need for monitors include the area between 10th Street and Ocean Avenue and between 2nd and 4th streets below Orange Avenue.
The weatherproof monitor made by PurpleAir is a small white device 3.5-by-3.5-by-5 inches in dimension. Installation can be in any secure exterior location with access to a continuous power source and wireless internet connection. Generous donations to Emerald Keepers have funded the purchase of the additional air-quality monitors so there is no cost to the homeowner to host a monitor.
Tim Rush, an Emerald Keepers board member, has hosted a PurpleAir device at his Coronado Cays residence for several years. “The device is truly plug and play. All that is needed is a sheltered location outdoors, a 110-volt outlet, and a Wi-Fi connection. The sensor is unobtrusive and has worked flawlessly for several years with no attention,” he said.
WORLD-WIDE TRACKING
PurpleAir has more than 22,000 active monitors across the globe that track and report five major air pollutants regulated by the federal Clean Air Act: ground-level ozone, particle pollution (also known as particulate matter), carbon monoxide, sulfur dioxide, and nitrogen dioxide. Particulate matter includes mold spores, dust, smoke, pollen, soot, and dirt. The sensors identify particulate matter between 0.3 microns and 10 microns in diameter, too small to be visible, but they cannot analyze the composition of particulates.
A real-time, interactive map of air-quality data from Emerald Keepers’ monitors can be viewed online at PurpleAir.com. The website’s color-coded map corresponds to the Air Quality Index, with values ranging between green (0, good) to red (500, hazardous). In 2025, Coronado’s air quality peaked at 162 AQI on Oct. 30 – an unhealthy level for everyone.
COUNTY MONITORS
The San Diego County Air Pollution Control District is the local government agency tasked with tracking air quality using monitors at eight sites across the county. The county’s closest monitor to Coronado is in Sherman Heights, which is east of Interstate 5 and south of state Route 94. The Apple weather app reports AQI data for Coronado based on the county’s air-quality monitor. Emerald Keepers monitors supplement the county program and provide hyper-local data specific to areas of Coronado.
If you are interested in supporting Emerald Keepers’ air-quality program by installing a PurpleAir device at your home, please contact [email protected].