Orange County NC Website
2 .2 Air Quality Monitoring Sites in Orange and Adjacent Counties <br /> The State of North Carolina Division of Air Quality is responsible for set up , <br /> maintenance , calibration, and operation of sites for monitoring air quality . The State does not <br /> monitor all of the criteria pollutants at all of its monitoring sites . Not all counties in the state <br /> have monitoring sites . The criteria for determining the locations of the monitoring sites vary by <br /> pollutant and depend on guidance given by EPA and the needs of the State of North Carolina to <br /> meet the requirements of the Clean Air Act . <br /> At this time , there are only two air monitoring sites in Orange County . Both sites are <br /> located in Chapel Hill . They include the following . <br /> • Carbon monoxide (CO) monitor - located at 147 East Franklin Street in Chapel Hill . CO <br /> is monitored on a seasonal basis from October to mid-March . This monitor has been <br /> operated for many years on a seasonal (fall/winter) basis . We have been advised by <br /> George Murray of the North Carolina Division of Air Quality that the monitor will not <br /> likely be run after this fall/winter season because ( 1 ) the EPA is working toward <br /> disinvestments in CO monitoring in the future, (2) the site is a " short-term" special <br /> purpose site , and (3 ) the CO concentrations are low . <br /> • Fine particulate matter (PM2 . 5 ) sampler - located at the U . S . EPA National Health and <br /> Environmental Effects Laboratory , 104 Mason Farm Road in Chapel Hill . Samples are <br /> collected for 24 hours every third day . The sampler was set up this year ( 1999) in <br /> response to the addition of PM2 .5 by the EPA to its list of criteria pollutants to be <br /> regulated under the Clean Air Act <br /> Because of the lack of monitoring sites in the County, there is little historical data on air <br /> quality in the County . Carbon monoxide, an air pollutant generated by combustion sources (e . g . , <br /> motor vehicles and power plants) , has been monitored in Chapel Hill for many years . But no <br /> other criteria pollutants have been monitored anywhere in the County . There are monitoring <br /> sites located in adjacent counties , which the State uses for assessing the air quality in the area. <br /> Table 2 -2 lists locations of monitoring sites and the pollutants that are measured in this region . <br /> There are no monitoring sites for ozone in Orange County . Ozone is a seasonal <br /> contaminant with the highest concentrations occurring in the summer . Ozone is not emitted from <br /> sources , but is formed by sunlight- driven reactions of other pollutants , especially hydrocarbons <br /> ides . Nitrogen oxides are released from nearly all combustion processes , <br /> and nitrogen ox <br /> including industrial boilers , open fires , and mobile sources . Hydrocarbons are released from <br /> mobile sources , industries , painting , dry cleaning , fuel dispensing , and natural sources . Ozone <br /> reaches its highest concentrations 3 to 5 hours downwind from major sources of the ozone <br /> precursors (nitrogen oxides and hydrocarbons) . The State does not intend to install an ozone <br /> monitor in Orange County . Based on our discussions with staff at the NC State Division of Air <br /> Quality, the State will use data from monitors in adjacent counties to assess the impact of reacted <br /> pollutant emissions from the city ( Chapel Hill/Carrboro) in the middle of the monitoring sites . <br /> There are ozone monitors northeast of Orange County and the Chatham monitor is to the south- <br /> 3 <br />