Glossary of Terms
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Continuous Emissions Monitoring System. 

Chart Recorders

In this millenium, chart recorders are becoming very digitized; actual "paper" based charts are being replaced regularly.  A digital chart can also print to paper (beit Z-Fold, circular, roll, etc.) but the real value of these newer recorders is that they can possess graphical screens which can show the process data in various formats and resolutions. Secondarily, the chart recorder stores the digital trend information for up to about 30 days (depending on the size of the internal memory) and then allows the data owner to 'dump' the data to a flash drive or download it to his internal network via Ethernet cable or wireless connection.



A method of detection where a chemical reaction generates a small amount of light(photons).  

This method is often used to measure total NOx.  The NO2 & NO3 within the sample gas is converted to NO via a heated carbon converter.  The NO is then mixed with O3 within a reaction chamber.  The amount of photons released during the reaction is proportional to the concentration of NOx in a sample stream. 


Continuous Opacity Monitoring System. 

Sometimes refered to as an opacity monitor, this system typically includes a transmissometer, purge air blowers, retroreflector, and control room electronics unit.  Pollutants and particals with the flu gas limit the light able to pass though the gas which yields an opacity reading.
Controllers, Boiler

Multi loop controllers typically used to control the fuel/air ratio in combustion processes.

Etalon analyzers

The means of differential gas absorption measurement where spectral correlation is removed by the use of an electro-optic modulator.

Fan/Damper Drives

All Hagan/Rosemount models.

Flame Ionization

Flame ionization is a method of detection used to measure total hydrocarbons (THC) in a gas stream.  


These units combine measurement "benches" utilizing several different principles of analysis (i.e., an NDIR, Thermal Conductivity, & an Oxygen cell can all be contained in the same unit).

NDIR (Non-Dispersive InfraRed)

This method of detection is based on the Luft detector. By passing infrared energy through a cavity of two cells (reference & measuring) to a non-linear detector (the Luft detector), the measurement is based on the difference in response of the detector with the gas-of-interest present in the cavity versus its response with no gas of interest in the cavity. The higher the difference, the higher the concentration of the gas-of-interest.


Opacity is the degree to which the transmission of light is reduced or the degree to which visibility of a background, as viewed through the diameter of a plume, is reduced.  A transmissometer (or opacity analyzer) measures the amount of light that is lost to scattering or absorption in the emission's effluent.  It is expressed in percentage usually, but sometimes in Ringelmann numbers.


This detection method is based on the effect of magnetic lines of flux on oxygen molecules. The oxygen molecules tend to pool around the high intensity flux lines.  A test body (a.k.a., dumb-bell), filled with nitrogen, is placed within the high intensity lines of flux; as the concentration of oxygen increases from 0.00% to 100.00%, the bouyancy of the nitrogen filled spheres increases as oxygen concentration increases.  The force developed by the bouancy is measured and a proportional signal is developed.


Oxygen concentration derived from a proportional current flow between the anode and cathode in an electrochemical cell.

Thermal Conductivity

Gases are measured by their ability to affect the transfer of heat away from the detecting heat source.

Trace Moisture

This measurement is based on the absorption and electrolysis of moisture in and electrolytic cell.

Transflectance (UV)

These analyzers use spectrally selective mirrors to isolate Ultraviolet spectral pass-bands prior to actual detection.

Zirconium Oxide

This method of analysis combines the ionization of O2 and a catalytic reaction between two platinum electrodes to produce a millivolt signal proportional to the concentration of O2 in the sample.