Oldies....and not so goodies

Plume opacity emission standards and requirements have played a key role in enforcement of federal, state, and local air pollution regulations. Failure to take these regulations seriously can be costly, as violations of opacity limits for air permits can result in up to $25,000 per source per day!

For decades, the most common method used to monitor opacity levels has been the EPA method 9 and 22 visual observation tests. Consistent economical compliance relies on a better understanding of these tests, how they related to legacy air permits in the past ,and how they will relate going forward. 

What are Method 9 and Method 22?

The revised EPA Method 9 was promulgated in 1974 as a replacement for the nearly 80+ year old Ringelmann system used previously to monitor and evaluate particulate emissions. These tests attempt to quantify opacity, which is essentially the obscuring power of the plume, expressed in percent. The more particles present in the plume the more light it will block from passing through. In addition to industrial applications where process gas is treated and then exhausted out of a stack, visible emissions standards are also applied extensively in controlling fugitive emissions in both industrial processes and non-process dust sources such as roads and bulk materials storage and handling areas. Often there are no convenient accurate stack testing methods for measurement of emissions from unconfined sources other than opacity methods. 

A method 9 test essentially is a planned observation of the stack conducted by a "smoke reader" - an individual certified to conduct the test per the guidelines in the EPA method 9 publication. During the test, the person observes the plume coming from the stack for a period of time, and makes an assessment of the visual opacity. In most cases, the observer will note the opacity every 15 seconds for 6 minutes and at times calculate an average opacity level over the overall time frame of the test. Method 9 outlines other guidelines to improve the observer’s ability to assign opacity values accurately.  These include the angle of viewing the source/stack, the location of the sun in relation to the observer and the source, the conditions during the test as well as background against which the plume is observed (e.g. different backgrounds and smoke combinations can make it more or less difficult for the observer, such as white smoke against a blue sky, or black smoke against a building in the background, etc.). After making these and other corrections based on the circumstance the observer records the overall opacity level. 

While method 9 is a quantitative test (as it attempts to measure opacity levels and thereby indirectly measure particulate concentrations), method 22 is a qualitative test used only to determine the presence or absence of visible emissions. Method 22 is conducted in much the same way as the method 9 test, but is less rigorous and does not require a person to be certified by an outside firm to conduct the test. Therefore, method 22 was intended for determining if a massive spike in emissions has occurred (such as a fabric filter baghouse with a broken filter). 

While methods 9 and 22 were standardized by the EPA over 20 years ago and many air permits have since incorporated them, the exact testing method required may differ depending on the applicable regulation. For example, depending on the circumstances the source could fall under the NSPS (New Source Performance Standards )a provision of a State Implementation Plan (SIP) or a site-specific compliance order/agreement conditions. (Note: Newer regulations such as Maximum Achievable Control Technology or MACT often require emissions so low that opacity observations are not capable of detecting them.) Before conducting any opacity observation test, compliance personnel should check the applicable regulation to ensure the correct method is used and what, if any, special procedures are called for by the regulatory agency. 

What Are They Used For?

For many decades, method 9 testing was the basis of all air permits in the United States. Depending on the permit, these tests were conducted at regular intervals (e.g. every 8 hour shift, daily, weekly, etc.), when changes were made to the process (e.g. new filters installed, new lines coming online, etc.), or to demonstrate compliance during permit testing. Method 22 in particular was frequently used when upset conditions occurred that potentially could have lead to a spike in emissions such as filter failure in the dust collector, fires, or other mechanical failures. 

These tests are also frequently used by government inspectors when in the field for quick diagnosis of emissions levels. In fact, most federal and state inspectors are required to be certified in method 9 and 22 observation standards. 

However, visual observations have their limits. In general, observers cannot detect opacity levels lower than 20%. Today, most industries are subject to PM emissions limits that are equivalent to less than 10% opacity. Additionally, some industries that fall under MACT standards, such as those with hazardous materials such as lead have even lower limits, meaning that by time the emissions became visually detectable the facility would have grossly exceeded its limits. 

Best Use of EPA Method 9 and 22 - Quick Reference and Backup for Other Monitoring Methods 

EPA Method 9 & 22 still have use today. True, they no longer form the basis for many plants air permits. However, they still can provide a quick way of providing relatively accurate assessment of particulate control efficiency. For this reason, many plants still retain some certified VE observers for use as backup monitoring option or for use during repairs or outages to their primary PM monitoring systems such as triboelectric broken bag detectors, bag leak detection systems, or opacity meters. Plants with air permits still based on method 9 and 22 observations, can be bogged down in the manual recording and time taken to regularly perform the tests. That is a main reason these test methods are quickly becoming obsolete and being replaced with newer air permits that mandate compliance with updated emissions limits and more accurate monitoring by means of continuous emissions monitoring systems or CEMS.  

For more information view the EPA quick guide to Method 9 and 22: https://www3.epa.gov/ttnemc01/methods/VEFieldManual.pdf

Does your facility still make use of Method 9 and 22 as its primary PM monitoring method? Click here to learn more about how modern triboelectric monitoring systems can help you more reliably achieve compliance as well as provide operational and maintenance savings.