Final Report: Micro-Discharge Based Multi-Metal Emissions Monitoring System

EPA Contract Number: EPD05059
Title: Micro-Discharge Based Multi-Metal Emissions Monitoring System
Investigators: Herring, Cy
Small Business: Caviton Inc.
EPA Contact: Manager, SBIR Program
Phase: II
Project Period: April 1, 2005 through June 30, 2006
Project Amount: $225,000
RFA: Small Business Innovation Research (SBIR) - Phase II (2005) Recipients Lists
Research Category: SBIR - Air Pollution , Small Business Innovation Research (SBIR) , Air Quality and Air Toxics


The objective of this Phase II research project was to develop design plans for a compact, sensitive, rugged, and low-cost multiple metals sensor to meet industry needs for metals monitoring. Metals monitoring faces increasing demands for lowering atmospheric emissions under Section 112(b) of the 1990 Clean Air Act Amendments, which aims to cut mercury emissions by 29 percent by 2007. Caviton, Inc., developed a multi-metals monitor based on micro-discharge technology by using atomic emission for metal identification and quantification. The targeted metals were cadmium, lead, mercury, nickel, and selenium, with an emphasis on mercury detection because regulations are more stringent for this metal. Current continuous monitoring instruments for emissions measurements for these metals either are prohibitively expensive (more than $60,000) or require frequent calibration by trained personnel, leading to high operating costs. Caviton developed a monitor at a much lower cost that is nearly ready for trial field testing. The monitoring systems are rugged (no moving parts), reliable, and inexpensive, allowing in situ monitoring in applications where cost has limited testing in the past.

Laboratory testing was preformed using proof-of-concept systems made of either quartz or stainless steel. Initial data are being collected on a prototype system that will be used for field trials. Several factors were evaluated in laboratory testing, namely detection limits (lower limit), dynamic range, and sensitivity to residual contamination of the detector from one analysis to another, which could limit the lower detection limits. Ultimately, a prototype detector was built and tested, and a customer was identified to pursue evaluation of the system further.

Summary/Accomplishments (Outputs/Outcomes):

Overall, results from experimentation showed that Caviton could produce a prototype instrument capable of simultaneous detection of mercury, cadmium, lead, and selenium in gaseous emissions from mobile and stationary sources. In fact, Caviton was able to design not only a prototype as part of the Phase II requirement, but built an operational prototype within the time and budget constraints of the Phase II project. Testing of the prototype has begun recently, but initial results show it will perform as expected. Additionally, the instrument does not have any moving parts nor does it use mercury lamps (as with many of the competing technologies), thus eliminating periodic replacement of these parts. Laboratory experimentation is summarized in Table 1 (the dynamic range was not tested on the upper limit for any metal).

Table 1. Detection Limits and Dynamic Range for Initial Part of the Phase II Project


Detection Limits

Tested Range

Dynamic Range

Hg (steel oven II)


1ng to 1µg


Cd (quartz oven)


1ng to 1µg


Pb (steel oven I)


30ng to 25µg


Se (quartz oven)


1ug to 20µg


*Results for nickel were inconclusive and not included in the table.

Caviton is optimistic that the prototype instrument can be installed in collaboration with a specific customer for continuous mercury emissions measurements in the process stream. Fine tuning the instrument in the field test will allow Caviton to manufacture products for this customer, leading to products for the open market.


Caviton developed a novel, rugged, low-cost, reliable instrument for the detection of a variety of metals, including mercury. These detectors constitute a platform technology that can be adapted to mercury detection in natural gas pipelines, smoke stack emissions monitoring, and field tests for environmental mercury. Adaptations to the instrument in the future also will allow the monitoring of pollutants such as NOx, SOx, CO, CO2, etc., as well as pesticides, herbicides, and chemical warfare agents. This instrument will allow sensitive monitoring of metals emissions at a cost far below available solutions, and are rugged enough to operate without maintenance for as long as a year or more in some cases. Caviton has targeted an initial niche market of mercury detection in natural gas pipelines that will allow growth of the company, the opportunity to branch out into other markets, and the application of this promising new technology.

Supplemental Keywords:

mercury detection, multi-metals detection, plasma discharge, micro-plasma monitoring, trace metals, emissions, micro-discharge light, spectrometer, smoke stacks, boilers, incinerators, continuous emissions monitoring, small business, SBIR,, RFA, Scientific Discipline, Air, Ecosystem Protection/Environmental Exposure & Risk, particulate matter, Air Quality, Environmental Chemistry, Monitoring/Modeling, Analytical Chemistry, Environmental Monitoring, Engineering, Chemistry, & Physics, particle size, monitoring, chemical characteristics, human health effects, aerosol particles, air quality models, HAPS, gas chromatography, air quality model, air sampling, ambient emissions, chemical detection techniques, emissions, metal speciation, particulate matter mass, particle sampler, human exposure, multimetal emissions, continuous emissions monitoring, arsenic speciation, spark induced breakdown spectroscopy, aerosol analyzers

SBIR Phase I:

Microdischarge-Based Multimetal Emission Monitoring System  | Final Report