AirLogic provides direct access to global air quality sensor networks

Government ground sensor networks have been around for years. Recently new citizen-science based ground sensor networks have also emerged. These networks powered by inexpensive ground sensors provide significant data around key sites and facilities. AirLogic provide access to these networks to allow you to see what is happening beyond your fence line and in the communities where you work.

In the case of AIRNOW, PURPLEAIR, and OPENAQ sensor networks in AirLogic, the default time period is hourly and the value displayed in the chart for a selected time is the hourly average of the selected metric. Setting the time period to daily/monthly/quarterly you can obtain a daily/monthly/quarterly rolling average for the selected metric.

Color Alerts: Table of Species

Once a site is selected, the Table of Species matches color-coded alerts for each species or measurement tracked in AirLogic.

The default color coding system is set up as an example in alignment with the alerts in My Map.

OpenAQ

OpenAQ is a non-profit organization empowering communities around the globe to clean their air by harmonizing, sharing, and using open air quality data.

Their repository of air quality now includes low-cost sensor data as a pilot, in addition to reference-grade data. Explore this data through the site or through the API, where all real-time and historical data is now accessible.

OpenAQ currently collects data in 130 different countries and primarily aggregate PM2.5, PM10, ozone (O3), sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and black carbon (BC) measurements. Additional pollutants outside of those standard sets of pollutants are now available through low-cost sensor sources at certain locations.

Open Air

AirNow reports air quality using the official U.S. Air Quality Index (AQI), a color-coded index designed to communicate whether air quality is healthy or unhealthy for you. When you know the AQI in your area, you can take steps to protect your health.

AirNow is a partnership of the U.S. Environmental Protection Agency, National Oceanic and Atmospheric Administration (NOAA), National Park Service, NASA, Centers for Disease Control, and tribal, state, and local air quality agencies. Complete list of AirNow partners.

Agencies all over the country send their monitoring data to AirNow for display. The Department of State provides data from U.S. Embassies and Consulates to inform personnel and citizens overseas, and the U.S. Forest Service and NOAA provide fire and smoke data.

Purple Air

PurpleAir sensors are used by a wide variety of individuals and groups from government air districts, school districts, and universities to industrial and commercial organizations to home enthusiasts and concerned citizens.

There are two major differences between PurpleAir sensors and regulatory sensors: the method of measuring particulate matter and the averaging time of the data collected.

Methods:

PurpleAir sensors use a laser particle counter to count the number of airborne particles in the air. That count is used to calculate a mass concentration, assuming an average particle density in an algorithm developed by the laser counter manufacturer, Plantower. An average density must be used because not all PM of a particular size is made of the same stuff. For instance, PM2.5 from wildfire smoke will have a different density than PM2.5 from dust blowing off a gravel pit. This means that mass concentration reported by a PurpleAir sensor can vary depending on the specific composition of PM for a given area thus making the sensors appear to “read high.” So far, two different research groups have completed studies for their areas and created conversion factors specific to the composition of particulates in their air: AQ&U and LRAPA.

Federal reference sensors typically measure mass concentration of PM by drawing air through a filter and weighing the filter. This method is expensive, difficult to install, requires a specialist to maintain the sensor, and reports on an hourly scale. Because of this, many cities have a limited number of these sensors (or none at all) and it’s not feasible for the general public to have their own.

Averaging Time:

PurpleAir uses the AQI breakpoints established by the US EPA to convert the mass concentration into the AQI published on the PurpleAir map. However, most regulatory groups report AQI as a 24-hour average that gets updated every hour or so. If you look at particulate matter data on a website like AirNow, a PM2.5 AQI of 150 means the average AQI in the last 24 hours was 150.

PurpleAir sensors use laser particle counters to count the number of particles in sizes from 0.3um up to 10um. These get converted into a mass concentration (ug/m3) and reported every 120 seconds. Since air quality can fluctuate greatly throughout the day, the real time PurpleAir AQI reading may appear “high” when compared to 24-hour averaged AQI data.