How does a Continuous Emission Monitoring System Work?

How does a Continuous Emission Monitoring System Work?

How does a Continuous Emission Monitoring System Work?

What is a continuous emissions monitor?

A continuous emission monitoring system is also known as a CEMS. This is a device that utilizes other devices to continuously measure the exhaust gasses for certain pollutants. These are recorded on a one minute basis and this ensures that the CEMS are operating in the correct way. CEMS systems have to be monitored closely to ensure that they are operating in the correct way. CEMS go through a range of tests with CEMS analyzer equipment necessary to perform regular calibration and continue performance testing.

All of our facilities work to measure nitrogen oxides, carbon monoxide and opacity as well as sulfur dioxide. Our operating permits are issued by state environmental agencies and this is under the authority by the US Environmental Protection Agency. The US EPA tells us what we need to measure and the CEMS work process allows the US EPA to compare performance data along the way against state emission limits.

How is CEMS data used?

Understanding how CEMS data work is important to know how it’s used. CEMS is used to determine whether emissions are correctly compliant with the permitted limits. The additional emissions data is gathered during the semi-annual or annual stack testing. This is done using the approved testing protocols and there has to be full compliance with these emission limits. These are then reported to the US EPA and other state environmental agencies.

The data that is posted is then reported to federal and state agencies on a quarterly, semi-annual and annual basis. If the data is over the permitted limit, the facility operators have to act quickly and address emissions that go above that limit. If there is a delay in posting data, there’s usually a reason behind it.

Reasons there may be a delay in posting CEMS data

Some of the permit requirements are established daily. We then have to wait until the day finishes before the average is calculated. The maximum results for the day – or at least the average – can be calculated then. Factors such as downtime monitoring, calibration requirements and backup monitoring can confirm data to ensure that it’s meeting the right reporting requirements. If all the data meets these requirements, it is then posted.

A CEMS provides us a way to monitor the gas emissions regularly and the CEMS draws out the exhaust gas sample from the stack, transports and then treats it for gas analyzers. The CEMS analyzer equipment then measures the concentrations of monitored pollutants and diluents in the samples. The CEMS is then provided with the right calibration gasses in the cylinders for the initial certification test, and the CEMS also collects and processes the pollutants for air quality management authorities.

Check “What does a typical CEMS consist of?” for more details about the CEMS equipment and components.