New Jersey Department of Environmental Protection

AQI Frequently Asked Questions

Data Download and Data Review

1. What is the difference between preliminary data and reviewed data?

Preliminary data are the initial hourly air measurements that have not yet been reviewed or edited and are subject to change. Reviewed data are finalized values that have been through a data review process. All data retrieved from this report generating tool is preliminary data. For reviewed data, please visit here.

2. Why does my air monitoring station have no current data?

There could be many external causes contributing to a lack of current data, such as inclement events causing disruptions of power to the station or communication from the station to the central database. Other causes of temporarily missing data include maintenance or service to an air monitoring station.

3. Why is ozone only measured during “ozone season”?

Ozone season refers to the period from March 1 to October 31 when the NJDEP is required by the U.S. Environmental Protection Agency (EPA) to measure ozone. In NJ, five stations operate during the ozone season, while eleven stations measure ozone year-round. Ozone is a secondary pollutant that is formed by the reaction of volatile organic compounds (VOCs) and nitrogen oxides (NOx) emitted by industrial sources and motor vehicles in the presence of sunlight and warm temperatures. During this season, warmer temperatures and sunlight are more prevalent thus causing higher ozone formation.

4. Why does the report only generate data for the last two years?

Our report tool only generates preliminary data collected within the past two years. To request data that is older than two years, please contact us here.

5. What is the AQI?

The Air Quality Index (AQI) is a uniform index for reporting daily air quality. It provides predictive information in real time on the local air quality, which includes the major air pollutants such as ozone, particle matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide. The AQI not only informs on the air quality, but also health advisories at ranges outside of “good” values.

6. What does the time stamp displayed with the data mean?

The time stamp, displayed as hh:mm 24-hour clock format (military time), refers to the start of the hour in Eastern Standard Time (EST). The data corresponding to this time stamp is the 1-hour average concentration of the pollutant collected during this 1-hour period. For example, a station reporting an ozone concentration of 0.065 ppm with a time stamp of 16:00 means the 1-hour average ozone concentration measured from 4:00 pm to 4:59 pm Eastern Standard Time is 0.065 ppm.

7. How can I download data?

You can download data from our AQI live map using the “Station Report” or “Multi Station Report” feature. To generate a report, select an air monitoring station, select an export format (table, excel or graph), and select “custom” period to enter desired timeframe.

8. Glossary of Units

Abbreviated Unit	Unit Name
ppm	parts per million
ppb	parts per billion
µg/m³	microgram per cubic meter

For more terms and definitions relating to air quality, please visit our glossary.

Exceedances and Advisories

1. What is an exceedance? Do they occur often?

An exceedance occurs when a value for any of the pollutants is measured above, or exceeding, the standard value. An exceedance does not immediately mean that there was a violation of the standard for that particular pollutant, because three years of data are needed to determine if the standard was violated.

2. Why is the AQI in my area higher than others?

Densely populated areas, with more motor vehicle traffic and more air pollution sources, may experience higher AQI levels than rural or less populated areas. Also, the direction of winds on a given day may carry air pollution to monitors downwind from air pollution sources while other monitors could be upwind from the same pollution sources and not measure any impact.

3. Are there times of the year when pollution is worse?

Generally, warmer seasons in New Jersey may experience worse air pollution. Exceedances for ozone can occur during the summer due to abundant sunlight and warm temperatures. Ozone is a secondary pollutant that is formed by the reaction of volatile organic compounds (VOCs) and nitrogen oxides (NOx) emitted by industrial sources and motor vehicles in the presence of sunlight and warm temperatures. Wildfires are also prominent in summer months, which can cause elevated particulate matter events in the state and/or region.

General

1. What are the six criteria pollutants? Where can I find more information about air pollutants?

The six criteria pollutants are particulate matter (fine particulates, PM2.5 and inhalable particulates, PM10), carbon monoxide (CO), ozone (O₃), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and lead (Pb). For more information about the six criteria pollutants, please visit here.

2. Why isn’t there a monitoring site in my area?

Monitoring stations are strategically placed throughout the state to meet certain objectives which include: provide publicly accessible timely data, support compliance with the National Ambient Air Quality Standards and provide air pollutant trends. The NJDEP conducts an assessment of the air monitoring network every five years, and submits a plan annually to the EPA to make sure the air monitoring needs are being met. Generally, stations are placed in communities most impacted by pollutants, with some being in rural areas to provide representative data of pollution upwind or downwind from urban areas.

3. Is there a glossary available with air quality and air monitoring terms?

Refer to our glossary here.

4. Any more questions or concerns?

Please fill out our contact us form for any questions.

Community Science

1. How can I use air quality sensors in my community?

Low-cost sensors are a more practical community approach to local air monitoring. They are portable, cost-efficient, and able to provide real-time measures of local air pollution. While the data provided by low-cost sensors are not as accurate as our equipment at air monitoring stations, this data is still very useful to community members because it can provide localized air measurements to supplement the NJDEP air monitoring network. To plan a community science project with low-cost sensors, please visit our community science website for guidance.

2. Does NJDEP have low-cost sensors that could be borrowed?

The NJDEP has a limited number of low-cost sensors that could be borrowed by organized groups for a short-term project depending on availability. The length of time for borrowing low-cost sensors is approved on a case-by-case basis. For more information, please view our community science website and contact us with any requests or questions.

3. What is community science?

Community science or “citizen science” refers to scientific research done by a collaboration of community members and scientists to provide meaningful data and insight into key issues. Community science projects prioritize the needs and issues of a community which can lead to recommendations for actions and policies that help advance the community.

4. What is the Youth Inclusion Initiative?

This NJDEP initiative provides participating youth (16-20 year old) nominated by host organizations with opportunities to develop some of the technical skills necessary to pursue a career in environmental protection in New Jersey. The program focuses on providing opportunities to youth from communities that have disproportionately less open space or historically lack natural lands access. More Info found here.