3 Types of Continuous Monitoring Systems

Posted by Radmin on May 13th, 2019

A Continuous Monitoring System or CMS is a tool that measures and records data and information from emission sources. The stored data, for example from NOx CEMS, is often used to operate the source and demonstrate compliance with certain regulations like the United States Environmental Protection Agency (EPA). EPA identifies 3 types of CMS. Continue reading to learn more about them.

Continuous Opacity Monitoring System

Continuous opacity monitoring system or COMS is used to measure a flue-gas' opacity that indicates the amount of light made obscure by a particulate matter in emissions. Emissions from opaque stacks will have 100% opacity and 0% transmittance. On the other hand, emissions from transparent stacks will have 0% opacity and 100% transmittance. This is mostly used by facilities that rely on coal, oil, wood, waste materials, or other fossil fuels for combustion.

Continuous Parametric Monitoring System

Continuous parametric monitoring system or CPMS is used to measure specific parameters and deduce emissions data from them. Parameters are the key indicator of a system's performance. They're generally an operational framework of the process of an air pollution control device or APCD. They affect the emission levels from the process or control efficiency of APCD. Parametric monitoring includes flow rate, pressure, and temperature monitoring.

Continuous Emission Monitoring System

Continuous emission monitoring system or CEMS is an instrument that directly measures emission levels from a stationary source. It measures the pollutant of concern or a surrogate for the pollutant concern from within a stack environment.

There are 3 methods used under CEMS:

•         Full Extractive Method includes acquiring representative portions of a gas stream and transports them to an analyzer.
•         Extractive Dilution Method includes extracting a very small portion of a gas stream, accurately diluting it with air before, and then transports it to an analyzer.
•         In-situ Measurement Method includes measuring and analyzing the gas directly at the desired point. An analysis is called in-situ point analysis if it's performed within close proximity of the instrument.

One of the most popular gases that are measured is nitrogen oxides with the use of Nitrogen Oxides CEMS or NOx CEMS. This monitors the emission level or concentration of the effluent from a source that must satisfy a NOx emissions limit. A CMS must be measured by specific criteria depending on the type of operation, which can include a formal certification by EPA.