Continuous Emissions Monitors (CEMs)

Pollutants which can be
continuously monitored (partial list)

Particulate Matter
Carbon Monoxide (CO)
Carbon Dioxide (CO2)
Nitrogen Oxides (NOx)
Nitrous Oxide (N2O)
Sulfur Oxides (SOx)
Hydrogen Sulfide (H2S)
Hydrofluoric Acid (HF)
Hydrochloric Acid (HCl)
Hydrogen Cyanide
Volatile Organic Compounds (VOCs)
Dioxins & furans
Polycyclic Aromatic Hydrocarbons (PAHs)
Vinyl Chloride Monomer

Most industrial facilities with combustion systems (incinerators, power plants, refineries, etc.) are not required to regularly test for most of the chemical pollutants they release. Facility operators will draw attention to the idea that they have continuous emissions monitors (CEMs), that engineers in a control room are constantly paying attention to their emissions, making sure they're within legal limits and that state regulators are hawkishly looking over the numbers and will fine the heavily if they exceed any limit. The reality is quite different.

Typically, only a few pollutants are tested continuously... usually Nitrogen Oxides (NOx), Carbon Monoxide (CO) and Sulfur Dioxides (SO2). Oxygen and various operating parameters like temperature are also typically monitored on a continuous basis. Sometimes continuous monitoring is required for opacity (an indirect way to measure particulate matter), hydrochloric acid or, more recently, mercury or particulate matter.

The most toxic pollutants are typically tested only yearly, if at all. Such infrequent testing (under ideal operating conditions) allows for easy manipulation of test results and is known to underestimate real emissions (see the Dioxin CEMs page for docmentation).

If we regulated motorists the way we do smokestacks, annual stack testing is like setting a speed limit and allowing drivers to drive all year with no speedometer. Once a year, on the highways, a speed trap would be set, with signs leading up to it warning 'slow down... speed trap ahead' ...and driver's brother would be run the speed trap (the companies do their own testing). In reality, smokestack facilities are 'speeding' many other days of the year, with excessive emissions during startup, shutdown and malfunction times, when testing is not done. Regulating air polluting facilities in this manner is inexcusable, especially in the age where continuous testing technology exists and where the data is able to be made available to the public real-time through a website.

Currently, the technology exists to continually monitor a long list of pollutants, including toxic metals, acid gases, dioxins, particulate matter and more (see sidebar).

Any corporation that claims that their facility's emissions will be within certain limits should be put to the test by asking that they install CEMs to provide real-time emissions data to back up their claims. All CEM data ought to be made available real-time on a publicly-available Internet website, as a condition of state permits. Where state agencies are unwilling to require such disclosure, local governments ought to pass laws to provide such requirements, as has been done with local ordinances in Pennsylvania.

CEM Equipment Verification:

Vendors providing CEM equipment: Long-term samplers for dioxin monitoring (AMESA):

International Conferences on Emission Monitoring:

Dioxin CEMs:

Permitted facilities required to use CEMs for Mercury:

Proposed facilities required to use CEMs for Particulate Matter (PM10):

The other two proposed waste coal-fired power plants planned for Pennsylvania would have also been required to use CEMs for PM10, but the southwest regional office of the PA DEP ignored comments by ActionPA and three federal agencies (U.S. EPA, USDA Forest Service and the National Park Service) and chose not to require this, as the northcentral PA DEP regional office did of the River Hill plant.

Here's where you can find the comments by the Forest Service and National Park Service on the waste coal power plant permits:
Comments on proposed waste coal facilities in southwestern Pennsylvania

Here's an excerpt from the National Park Service comments on the Greene Energy Resource Recovery Project:

"Compliance Monitoring

We recommend that a filterable PM10 limit and Continuous Emissions Monitor (CEM) requirements be added. For example, the West Virginia Division of Air Quality (WVDAQ) has included both filterable and condensable PM10 in its permit limit for Longview Power, and proposed that PM emissions be monitored by a CEM within 18 months of boiler start-up or when performance specifications for such monitors are promulgated, whichever comes later.[1] We continue to believe that CEMs are an important tool for monitoring compliance. For that reason, we recommend that a PM CEM be installed upon startup.

[1] Those CEM Performance Specifications were later promulgated by EPA on 1/12/04."

EPA's comments submitted on 3/11/2005, were as follows:

"The proposed plan approval requires annual stack testing to assure compliance with the particulate matter emission limits from the CFB and its associated fabric-filter baghouse. In light of the evolution of CEMS systems for particulate matter, EPA is strongly urging the requirement to install and operate a particulate matter CEMS at the proposed facility. Currently, there are several facilities that operate PM CEMS and have demonstrated that the systems are reliable and accurate. These are Tampa Electric power plant (Florida), Eli Lilly Corporation (Indiana), and the U.S. Department of Energy (Tennessee). EPA has also secured commitments from up to 30 existing coal-fired utility installations to install PM CEMS over the next couple of years. It is fair to assume that the state of technology for PM CEMS will be even further evolved by the time the proposed Robinson Power facility begins operation. Further, the facility will be required to establish a compliance assurance monitoring plan (CAM) as part of its title V operating permit and the federal CAM regulations strongly encourage reliance on continuous monitoring systems as a means for assuring compliance. Also, the upcoming re-designation of the area to nonattainment for PM2.5 suggests that more timely and accurate data regarding PM emissions from the proposed facility would be important information."