Monitoring Air Pollution

What standards are used for monitoring air pollution?

The EPA uses monitors/analyzers/ samplers that comply with the Federal Reference Method (FRM) or equivalent method (FEM) to measure the criteria pollutants for compliance to NAAQS. These devices undergo rigorous testing and calibration and cost tens of thousands of dollars.

In recent years, the government is driving the commercialization of low-cost sensors (less than $1000) to facilitate the reliable, real time collection of air pollution data. In order for these devices to perform adequately for air pollution monitoring that meets NAAQS, the FEM is applied to evaluate new sensors in both laboratory and field conditions. These sensors use a variety of technologies: electrochemical, metal oxide, spectroscopic, and particle. Each have their strengths in measuring specific pollutants at specific concentrations.

Sensor TypePollutants Measured (criteria)
RangeInterferences [IF]
Electro-chemicalCO, SO2, NH3, H2S1 ppb to 10-1200 ppmSO2 [IF]: Cl, CO, H2O(g), C3H8, C4H8, C7H8fixed/hand-held/portable
Metal oxideNon-CH4 hydro-carbons (NHMC), C6H6, CH4, total VOCs, NH3, CO, NO2, SO2, NOX0.1 to 25-100 ppm (1 ppb?: NO2, CH4, C6H6)CO [IF]: H2O(g), CO2, H2fixed/hand-held/portable
SpectroscopicNO (chemi-luminescence [CL]), CH4, VOCs (non-dispersive infrared: NDIR)9 ppb (CL) or 1-100% (NDIR)NO [IF]: H2S, CO2, O3, H2O, NO2, SO2, NH3fixed/hand-held
ParticlePM to 0.5 micron particle size: light scattering) (> 0.16 μg/m3: Light absorption measurement [density])0.1 to 0.5 microns (scattering) > 0.16 μg/m3 (absorption)N/Ahand-held

Summary: Sensor Types and Characteristics (Source: EPA)

These new sensors are enabling the public to understand their air quality better. These sensors not only give citizens the ability to detect and measure pollution in the environment but to help them understand the linkages between their health and the environment. For example, real-time information from the sensors combined with location data can provide individualized assessment of exposure.

The confluence of low-cost sensors, information infrastructure, and analytical tools is giving researchers more capacity to study the dynamics of air pollution at the local, regional, and global scales. In addition, these devices are portable and can be used to track mobile (vehicle) emissions that could not be done with conventional monitors.