Inductively coupled argon plasma continuous emissions monitor for hazardous air pollutant metals

The design and operation of instrumentation capable of continuous, real-time detection and monitoring of hazardous air pollutant metals in the effluent of boilers, incinerators, and furnaces is reported. A commercially available inductively coupled argon plasma spectrometer, modified for introduction of sample air, provides sensitivity for several metals comparable to that of EPA-approved manual methods, with a measurement frequency of 30-60 measurements/h. Achievable detection limits for the present list of hazardous air pollutant metals range from 0.1 to 20 mu g/dry standard cubic meter; a capability unmatched by competing CEM technologies. To ensure that a representative sample is obtained at all times, air is isokinetically extracted from a stack or duct by an automated system. An innovative sampling interface combines continuous sample extraction at the relatively high and often variable flow rates required for isokinetic conditions with periodic introduction of aliquots of sample air and reference air at the constant and low flow rates required for injection into the argon plasma.