Is Triboelectric Stack Monitoring an Alternative to EPA Method 9?

Posted by Earl Parker on Aug 30, 2017 2:35:00 PM

Best Reasonable Solution for Emissions Monitoring

Many plants continue to use EPA Method 9 visual observations as their primary dust collector monitoring methodology. Even as newer plants have already moved on to modern monitoring technologies, such as triboelectric dust monitoring, these plants continue to hold fast to their Method 9 CAM plans. Does triboelectric dust emissions monitoring really provide a realistic alternative to visual observation? In many cases, visual observations were the most accurate and feasible solution at the time the air permit was written. And many are still following this method today. But technology has advanced significantly and today visual observation is less reliable, less accurate and substantially more labor intensive compared to electronic instruments.

The Original Purpose of EPA Method 9

Method 9 was developed to improve opacity monitoring in the 1970s as the Clean Air Act came into existence and more effective monitoring schemes were needed. It serves as a quantitative test that attempts to determine the amount of particulate concentration in the stack plume (compare with EPA Method 22 - a less rigorous testing process that serves as a qualitative test to confirm the presence of a high concentration of particles indicating a failure of the control system). Method 9 proved an improvement on earlier emissions observation methods, such as the Ringelmann system used from the late 19th century until 1974. The method sets guidelines for how an observer can conduct the observation in such a way so as to reduce observer bias and improve reliability. Method 9 requires personnel to receive training at an EPA accredited institution. 

Limitations of EPA Method 9 epa method 9 made sense when it was introduced but today triboelectric stack monitoring is a better solution

Visual observations were developed at a very different time with very different emissions standards. The past 40+ years have seen major changes to emissions limits of all types, especially PM and specific materials. PM 2.5 now replaces PM 10 in most applications with overall limits for both much lower than in 1970s. Many industries now find themselves subject to specific MACT standards that call for even stricter PM limits. 

The problem lies in the inherent inaccuracy of visual observations of opacity. Even under ideal conditions, observers can only note opacity once it passed 10-20%. To reach this level, most industries will have to emit far in excess of their PM limits. Therefore, by the time a well trained observer, working in perfect conditions can even see an increase in opacity, the plant has already likely violated its emissions limits. The reality is that Method 9 no longer serves as a regular monitoring option, but really only as a backup compliance monitoring method during maintenance or issues involving the primary monitoring system. 

Advantages of Triboelectric Stack Monitoring Over EPA Method 9 Observations

Remote monitoring completely eliminates the need for manual observations. No need to have certified personnel on hand at all times and no more costs associated with sending key personnel to “smoke school” every few years. Also, triboelectric data can be fed directly into a central reporting system thereby eliminating the often tedious clipboard data entry process so often involved with fully manual monitoring methods. 

Further, the more accurate triboelectric dust monitoring can detect PM concentrations as small as 0.000002 g/dscf. Many times more sensitive than even the best opacity meters (not observers) on the market today! This means operators can see problems as they form in their earliest stages and take appropriate corrective action. In addition, the trending emissions data can be useful for a wide range of other uses to help improve efficiency, cut operating costs and more carefully control emissions. These and other predictive maintenance capabilities mean triboelectric systems provide potentially huge cost savings, both direct and indirect to plants. 


Increased accuracy, lower labor and training costs, predictive maintenance capabilities and greatly improved reliability all add up to triboelectric dust monitoring proving more than adequate alternative to EPA Method 9 monitoring. 

Would you like to know how your plant can move beyond Method 9 monitoring and gain the benefits of triboelectric dust monitoring? Click here to contact us and receive a free consultation! 

Baghouse Maintenance Checklist

Are you responsible for compliance monitoring, dust collection and baghouse maintenance at your facility? Check out our handy baghouse maintenance checklist that provides guidelines for daily, weekly, monthly, quarterly and annual preventive maintenance steps.

Topics: Air Permits, Triboelectric Detection, Environmental Monitoring