Carbon Monoxide
Carbon monoxide (CO) is a colorless, odorless, highly toxic gas emitted from automobiles. In small amounts it can impair alertness and cause fatigue and headaches. In large amounts it can kill. People with heart conditions and respiratory ailments are especially susceptible.
Carbon monoxide is monitored continuously by analyzers that operate on the infrared absorption principle. Ambient air is drawn into a sample chamber and a beam of infrared light is passed through it. CO absorbs infrared radiation and any decrease in the intensity of the beam is due to the presence of CO molecules. This decrease is directly related to the concentration of CO in the air. A special detector measures the difference in the radiation between this beam and a duplicate beam passing through a reference chamber with no CO present. This difference in intensity is electronically translated into a reading of the CO present in the ambient air, measured in parts per million.
Carbon Monoxide Fact Sheet
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Ozone
Ozone is formed when nitrogen oxides and certain hydrocarbons, produced mainly from automobiles, combine in the presence of sunlight. Ozone is one component of photochemical smog. It can affect the tissues in plants and is irritating to the eye, nose, throat and respiratory system.
Ozone is measured continuously by analyzers that operate using the monochromatic ultraviolet absorption spectrophotometry principle. As ultraviolet light at 253.7 nanometers is passed through the optic bench, a fixed quantity of zero air and ambient air are drawn into the bench. The intensity of the ultraviolet radiation traversing the optic bench is attenuated by the ozone present in the ambient sample. This attenuated signal is detected and compared with the unattenuated signal from the zero air cycle. This difference in intensity is electronically translated into a reading of ozone present in the ambient air.
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Sulfur Dioxide
SO 2 , sulfur dioxide, is a heavy pungent, colorless gas formed primarily by the combustion of fossil fuels. Sulfur dioxide can affect the respiratory tract, as well as vegetation and other materials. Coal, with high amounts of sulfur, must usually be cleaned before or during burning in order to meet clean air standards.
Sulfur dioxide is measured continuously by instruments using the fundamental principle of fluorescence. Fluorescent analyzers irradiate an ambient air sample with ultraviolet light at 213.8 nanometers. Sulfur dioxide gas molecules absorb a portion of this energy, then re-emit the energy at a characteristic wavelength of light. The light energy emitted by the SO 2 molecules is sensed by a photomultiplier tube and converted to an electronic signal proportional to the concentration of SO 2 present.
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Particulates
Particulates are very small solid or liquid particles in the air. They can aggravate respiratory disease, reduce sunlight, and damage plants. Particulates can be found in dust, smoke, fumes, mist, spray, and fog. The major sources are iron and steel operations, electric power generation, and coal burning operations.
PM10 is defined as particulate matter with an aerodynamic diameter less than or equal to a nominal 10 micrometers. The reference method for the measurement of atmospheric particulate matter is based on selection of PM10 particles by internal separation, followed by filtration and gravimetric determination of the PM10 mass on a filter substrate. Selection of PM10 is accomplished by a size selective head that is symmetrically designed and contains nine circular acceleration nozzles. By virtue of their larger momentum, particles greater than 10 microns aerodynamic diameter impact onto a greased implication shim. The particles smaller than 10 microns are carried vertically upward by the air flow and down sixteen vent tubes to a 8 by 10 inch quartz-fiber filter, where they are collected.
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