Metals and Mercury Testing - EPA Method 29

A metal emissions result is only as defensible as the sample behind it. Metals and Mercury Testing - EPA Method 29 is designed to measure particulate and gaseous metal emissions from stationary sources using a controlled sampling and analytical process. For facilities with permit limits, source-test obligations, or emissions inventories, the method provides data that must stand up to regulatory review.

EPA Method 29 is commonly applied to combustion sources, boilers, heaters, cement operations, manufacturing processes, and other industrial exhaust streams where trace metals or mercury may be present. The testing program must account for the source conditions, applicable permit language, required averaging period, and reporting format before a field crew arrives on site.

What EPA Method 29 Measures

EPA Method 29 determines emissions of a defined group of metals from stationary sources. The analyte list can include antimony, arsenic, barium, beryllium, cadmium, chromium, cobalt, copper, lead, manganese, mercury, nickel, phosphorus, selenium, silver, thallium, and zinc.

The applicable analyte list is not always the full list in the method. A permit, approval, compliance order, or project objective may identify only selected metals. Establishing that scope early prevents unnecessary laboratory work while ensuring the final report addresses the actual compliance requirement.

Method 29 generally reports total chromium, not hexavalent chromium. Where a requirement specifically addresses chromium VI or another metal species, a separate method and sampling strategy may be needed. This distinction matters because total-metal data cannot be assumed to represent a specific chemical form.

Why Isokinetic Sampling Matters in Metals and Mercury Testing

Many regulated metals are carried on particulate matter. EPA Method 29 therefore uses isokinetic sampling, meaning the velocity of gas entering the sampling nozzle is matched as closely as practical to the velocity of gas in the stack. If the sampling rate is too low or too high relative to stack velocity, particles can be under-collected or over-collected, affecting the reported concentration and emission rate.

A compliant test begins with accurate source characterization. Stack dimensions, traverse points, gas velocity, temperature, moisture, oxygen or carbon dioxide, and molecular weight are established through the appropriate supporting methods. These measurements are not administrative details. They determine nozzle selection, sampling rates, test duration, and the validity of the final metals result.

The sampling train is configured to capture metals in both particulate and vapor phases. A heated probe and filter assembly collect particulate-bound material, while downstream impingers collect compounds that pass through the filter. Mercury requires particular care because it can occur in forms that are not reliably represented by filter catch alone.

Field Controls That Protect Data Quality

Method 29 testing requires disciplined execution before, during, and after each run. Leak checks, calibration records, train assembly, reagent preparation, sample recovery, and chain of custody all contribute to whether results are defensible.

Field teams must also manage practical operating constraints. Variable load, unstable fuel conditions, poor access, high stack temperatures, and limited outage windows can affect the test plan. Testing should be scheduled during representative operation unless the permit or regulator specifies another condition. A technically correct sampling train cannot compensate for data collected during an unrepresentative operating period.

For facilities subject to multiple obligations, it can be efficient to coordinate metals testing with related stack testing, including particulate matter, acid gases, combustion efficiency, or flow characterization. The combined program must still preserve each method's required configuration and operating conditions. Combining work is useful only when it does not compromise data quality or regulatory acceptance.

Laboratory Analysis and Reporting Considerations

After recovery, collected samples are preserved, prepared, and analyzed using the laboratory procedures specified by the method or project requirements. Metals may be analyzed by techniques such as inductively coupled plasma spectroscopy or mass spectrometry, while mercury requires a suitable mercury-specific analytical approach.

The final report should clearly identify the sampling location, process conditions, test dates, methods used, laboratory results, blank results, quality-control information, and calculated concentrations and mass emission rates. Units must match the applicable permit or reporting requirement. A result in milligrams per dry standard cubic meter is not interchangeable with an hourly mass rate without the supporting flow and moisture calculations.

Detection limits also deserve attention during planning. A facility with very low expected emissions may need longer sampling durations, larger sample volumes, or laboratory methods capable of achieving reporting limits below the applicable threshold. A non-detect result is useful only when its reporting limit is appropriate for the compliance decision.

Planning an EPA Method 29 Test Program

A successful program starts with a review of the governing requirement, source operating range, target compounds, and required test conditions. Environmental and operations teams should confirm the process configuration, fuels or raw materials in use, control-device status, access readiness, and any scheduled operational changes that could influence emissions.

For industrial facilities, Method 29 is more than a sampling exercise. It is a coordinated measurement program that connects field execution, laboratory quality assurance, emissions calculations, and compliance reporting. Early technical planning gives the testing team the best opportunity to produce reliable results that support permit obligations and operational decisions.