Commerce City-North Denver
Air Monitoring


Suncor Energy (U.S.A.) Inc. (Suncor) committed to developing an enhanced air monitoring program in response to community feedback received in late 2020. CCND Air Monitoring was established in a coordinated and collaborative manner with existing air monitoring networks in the area. Throughout the development process, Suncor met with regulators and other government stakeholders to help shape the program, including Colorado Department of Public Health and Environment, Commerce City, City and County of Denver, Adams County and Tri-County Health Department. Furthermore, Suncor held two public meetings in May 2021 to provide the community with an opportunity to help shape CCND Air Monitoring. At the meetings, community members learned more about air monitoring and provided input in the program, including where additional air monitors should be located.

Suncor selected Montrose Air Quality Services, a third-party team of environmental experts, to deploy, operate and maintain the program.

Montrose’s air quality division is one of the largest air quality measurement groups in the world and specializes not only in the measurement of air quality, but also the development and evaluation of emerging technologies for conducting these measurements. With an office in Denver’s Sunnyside neighborhood, Montrose was also selected based upon their extensive experience conducting similar air monitoring programs including Denver’s “Love My Air.”
Suncor Energy (U.S.A.) Inc. is providing the funding for Montrose Air Quality Services (Montrose) to deploy, operate and maintain the program, and for Montrose and its subcontractors to share the data publicly.
Air monitoring is the measure of ambient air pollution levels in a particular area using various technologies and analysis methods.
The program monitors the air using three different methods:
  1. Continuous air quality sensors that are permanently positioned at 10 locations within the surrounding communities. The data from these sensors are provided on the website in near real-time. In-depth reports containing health risk analysis and quality assurance results are provided on a quarterly basis.
  2. Summa canisters are used to collect air samples that are then analyzed in a lab. Summa canister collections are automatically triggered when our continuous air sensors have a total volatile organic compound reading above 1 ppm for 1 minute. Montrose also plans summa canister collection once per quarter at all 10 community monitoring locations plus 3 additional locations far north and south of the CCND area to collect additional data for use in the health risk analysis. These results are shared in reports as soon as the data is available for the triggered samples, and shared quarterly for the planned summa canisters.
  3. Mobile lab air monitoring measures the air quality while driving up-and-down streets in the residential neighborhoods in the CCND area. Quarterly, the mobile lab monitors the neighborhoods (day or night) by collecting a data point every second at ultra-low levels. The results from the mobile lab monitoring campaigns are shared in quarterly reports.

The program will provide near real-time data to the public for the following compounds: carbon monoxide (CO), sulfur dioxide (SO2), hydrogen sulfide (H2S), nitrogen dioxide (NO2), particulate matter (PM2.5), and total volatile organic compounds (VOCs).

In addition, the CCND Air Monitoring program will intermittently deploy a mobile lab (van) as well as collect air samples (summa canisters) that are analyzed in a lab for the following VOC compounds:

Propane 2-Methylhexane Ethane Methyl-cyclopentane o-Ethyltoluene (2-ethyltoluene)
1,3-Butadiene 2-Methylpentane Ethylbenzene m-Ethyltoluene (3-ethyltoluene) p-Diethylbenzene (1,4-diethylbenzene)
1-Butene 3-Methylheptane Ethylcyclohexane1 m/o/p-Xylenes p-Ethyltoluene (4-ethyltoluene)
1-Hexene 3-Methylhexane Ethylene n-butano 1,2,4-trimethylbenzene
1-Pentene 3-Methylpentane Hydrogen Cyanide1 n-Decane Propylene (Propene)
Styrene1 Acetylene Hydrogen Sulfide1 n-Dodecane 2,2,4-Trimethylpentane
2,2-Dimethylbutane Benzene i-Butane n-Heptane Tetrachloroethylene
Toluene Carbon disulfide i-Pentane n-Hexane 2,3,4-Trimethylpentane
2,3-Dimethylbutane trans-2-Butene Naphthalene2 n-Nonane trans-1,2-Dimethylcyclohexane1
2,3-Dimethylpentane cis-2-Butene Isoprene n-Octane trans-1,3-Dimethylcyclohexane1
2,4-Dimethylpentane cis-2-Pentene m-Diethylbenzene (1,3-diethylbenzene) n-Pentane cis-1,3-dimethylcyclohexane1
2-Methyl-2-butene1 Cumene1 Methanol1 n-Propylbenzene trans-2-Pentene
2-Methylheptane Cyclohexane Methyl-cyclohexane n-Undecane Cyclopentane
1,2,3-trimethylbenzene2 1,3,5-trimethylbenzene2 i-Propylbenzene2 Neopentane (2,2-dimethylpropane)1 o-Diethylbenzene (1,2-diethylbenzene)1
1Only analyzed for with the mobile lab
2Only analyzed for with summa canisters

According to the CDC Agency for Toxic Substances and Disease Registry, an acute exposure is defined as contact with a substance that occurs only once, or for only a short time (up to 14 days), while chronic exposure is contact with a substance that occurs over a long time (1+ year).

In the screening level health risk evaluations, toxicologists at CTEH look at both acute and chronic exposures by reviewing the air data collected over a short and a longer period of time. The air data is compared to either acute or chronic health-based reference levels, which are generally set at levels that are likely to be without an appreciable risk of adverse health effects, even for sensitive sub-populations.

No, this monitoring network was not established on the basis of a federal, state, or local requirement or mandate. The program was developed in response to feedback from the community last fall. Suncor Energy (U.S.A.) Inc. decided to develop an enhanced air monitoring program in the Commerce City and North Denver area in collaboration and cooperation with other regional air monitoring initiatives.

Some general characteristics for different sensors are:

Particulate Matter 2.5 (PM2.5)

  • Laser scattering
  • Sensitivity to relative humidity and temperature

Nitrogen dioxide (NO2)

  • Electrochemical
  • Electrochemical sensors sensitive to O3 and temperature

Sulfur dioxide (SO2)

  • Electrochemical or metal oxide sensors
  • Electrochemical sensors sensitive to temperature and cross-interferences
  • Sensitivities are often not low enough for typical ambient air concentrations

Carbon monoxide (CO)

  • Electrochemical
  • Electrochemical sensors sensitive to temperature and cross-interferences
  • Sensitivities are often not low enough for typical ambient air concentrations

Volatile organic compounds (VOC)

  • Photo ionization detectors
  • Provide a total VOC reading only, not individual compounds
  • Sensitive to humidity
  • Sensitivities are often not low enough for typical ambient air concentration

Additional Resources:
CDPHESensorGuidanceFactSheet08262019.pdf (
Monitoring Technology

Historically, air monitoring had been performed using very expensive, large equipment that needs to be operated in a weatherproof, temperature-controlled environment with access to electrical power. Air sensor monitors are lower in cost, portable, easier to operate and maintain, and are widely being used for community monitoring programs, including by government agencies in Colorado. With the ability to easily place the monitoring equipment, we can create a more localized network of instrumentation to measure the air quality within the community.

Additional Resources:
Air Sensor Toolbox | US EPA
CDPHESensorGuidanceFactSheet08262019.pdf (

The gas (CO, NO2, H2S, and SO2) measurements data displayed on the website are updated every 5 minutes and are presented on a 60-minute rolling average concentration basis. The PM2.5 measurements data displayed on the website is updated every 60 minutes and are presented on a 60-minute rolling average concentration basis.

The sensors report data at least once every 5 minutes to the data management system. While the 5-minute data values can be interesting, there can be more variations in the values. Therefore, the gas (CO, NO2, SO2, and H2S) data presented on the website are 1-hour rolling averages, which are updated every 5 minutes, to provide a more representative value. The PM2.5 data presented on the website is a 1-hour block average to align with the other PM2.5 sensor-based monitoring programs around the local community. The National Ambient Air Quality Standards, which are health-based, are generally 1-hour, 8-hour or 24-hour average standards, so a short-term reading (such as 1 minute) cannot be directly compared to an air quality standard.

Summa canisters are collected over both a 1-hour period and 7-day period. The acute health-based reference values used in this program are based on a minimum of 1-hour of exposure. The 7-day samples are only used in the chronic health risk analysis report and are conservatively compared against health-based reference levels that are based on lifetime exposure.

Acute Exposure Level Guidelines (AEGLs) are used by emergency planners and responders worldwide as guidance in dealing with rare, usually accidental, releases of chemicals into the air. AEGLS are expressed as specific concentrations of airborne chemicals at which health effects may occur. They are designed to protect the elderly and children, and other individuals who may be susceptible.

AEGLs are calculated for five relatively short exposure periods — 10 minutes, 30 minutes, 1 hour, 4 hours, and 8 hours — as differentiated from air standards based on longer or repeated exposures. AEGL “levels” are dictated by the severity of the toxic effects caused by the exposure, with Level 1 being the least and Level 3 being the most severe.

The AEGL-1 60-minute values for H2S (510 ppb), NO2 (500 ppb), and SO2 (200 ppb) presented on the website are the most conservative exposure values for the 60-minute concentrations. The EPA did not derive an AEGL-1 value for CO, therefore an AEGL-2 (83 ppm) was selected.

More information about EPA’s AEGLS can be found here.

The Clean Air Act, which was last amended in 1990, requires EPA to set National Ambient Air Quality Standards (NAAQS) for six principal pollutants (”criteria“ air pollutants) that can be harmful to public health and the environment.

The Clean Air Act identifies two types of national ambient air quality standards. Primary standards provide public health protection, including protecting the health of ”sensitive“ populations such as asthmatics, children, and the elderly. Secondary standards provide public welfare protection, including protection against decreased visibility and damage to animals, crops, vegetation, and buildings.

The data presented on the trends should only be used for information purposes against the standards. Please reference the data collected by the Colorado Department of Public Health and Environment (CDPHE) for regulatory decision making here.

Additional Resources:

To ensure the data is of the highest quality, Montrose developed a Quality Assurance Project Plan (QAPP). The QAPP is a written document outlining the procedures a monitoring project will use to ensure the data it collects and analyzes meets project requirements. A QAPP helps the data user and monitoring project leaders ensure that the data collected meet their needs and that the quality control steps needed to verify this are built into the project from the beginning. Local regulatory and government agencies also reviewed the CCND Air Monitoring QAPP. A copy of the QAPP can be found here on the website.

The data on this dashboard is only primary or raw data. The near-real-time data displayed on this website are raw data that have not passed through the rigorous quality control required for data to be considered ”final.“ Data is considered preliminary for one quarter (90 days) to allow time to complete quality control checks, finalized, and posted on the site.

You can access quarterly valid data through the “Documents” page on this website.

Some of the measured compounds can have strong smells (for example, H2S and VOC), the smell does not necessarily indicate that the compounds are present in the air at levels of concern.

Real-time data may be invalidated when the quality of the data is in question or could be inaccurate, which could happen for a number of reasons.

For example, in extreme heat and low humidity AQMesh electrochemical sensors on the air monitors go into what is called an “extreme environment” mode, indicating that the data the sensors are gathering may not be reliable. Sensor output returns to normal when conditions are less hot and dry.

The extreme environment flagging forms part of AQMesh sensors’ internal quality assurance and quality control procedures. It is devised to ensure optimal data quality and confidence in data. Extensive research with datasets comparing co-located AQMesh sensors and regulatory grade instruments has been used to identify the conditions under which the sensor response changes and the “extreme environment” flag is applied.

More information around data validation can be found here within the Quality Assurance Project Plan (QAPP).

To learn more about compounds being monitored, see the “Compounds” and “Definitions” sections here.

For more information on Acute Exposure Guideline Levels, visit EPA’s AEGL website

For additional information on air monitoring sensor technology you can visit EPA Air Sensor Toolbox | US EPA