Once a monitor collects data, it is sent to the NCDAQ and its partner agencies. Fine particle pollution collected on the filter will reduce (or “attenuate”) the amount of beta particles that can pass through to be measured on the other side, and therefore the mass of the particulates can be determined (the second image depicts this process). A small amount of high-energy electrons (beta particles) is emitted before the air passes through the filter ribbon, and there are sensors that measure these particles both before and after passing through the filter ribbon. Ambient air is drawn through a ribbon of filter material, where the fine particulates collect. Monitors that measure concentrations of fine particle pollution often utilize a technique called beta attenuation monitoring, or BAM for short. Since the infrared light will be absorbed differently depending on how much gas is present in the air sample, the sensor can see the difference between the two chambers and determine the concentration of the pollutant in question. They consist of two chambers – one which has a known concentration of gas, and another with a sample of ambient air (i.e. Monitors that report gaseous pollutants often use an infrared sensor to determine the concentration in a given sample. Pollutants such as oxides of nitrogen, sulfur dioxide, carbon monoxide, and ozone are all gaseous pollutants, whereas fine particle pollution is made up of small particulates. There are a few different types of monitors, depending on what pollutant is being analyzed. Additionally, there are air quality monitors for nitrogen oxides, sulfur dioxide, and carbon monoxide across the state, and as of 2021 there are two sites that have a Photochemical Assessment Monitoring Station (PAMS) that measure levels of ozone precursors. NCDAQ and its partner agencies have deployed monitors for several pollutants, including ozone and fine particle pollution (the two pollutants the DAQ prepares forecasts for). There are 38 sites operated by NCDAQ, five operated by MCAQ, three operated by Forsyth County, and three operated by WNC. The current North Carolina monitoring network consists of 75 monitors across 49 different monitoring sites. Every year, the monitoring network is re-evaluated to ensure there is adequate coverage, with a complete network assessment performed every five years to anticipate future needs. These monitors are in a variety of locations and help determine population exposure, maximum concentrations, background concentrations, and regionally transported air pollution.
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