Source testing is a common method for determining the direct emissions from a piece of equipment. There are many reasons you might want to conduct a source test (also sometimes called a stack test), and the results can have a number of different uses, including:
- Demonstrating that your equipment meets the emission requirements of a certain rule
- Collecting data from the actual operation of your equipment to use for permitting or for other special studies
Whatever your reason for conducting a source test, you’ll want to keep the following five points in mind.
Remember that not all of these points are applicable to every situation, since each project will have different requirements.
1. Some regulatory agencies have their own required source-testing methods.
For any given piece of equipment, there can be numerous methods to measure its emissions, and each method is likely to produce different results. To eliminate such discrepancies, regulatory agencies often outline which testing methods must be used for their specific reports. Providing hard and fast requirements ensures that the samples are collected accurately and uniformly.
A list of EPA source-testing methods can be found here. Local air agencies might require test methods that differ from the EPA’s. For example, the AQMD lists source-testing methods that must be used if a test is being completed for their purposes. So if you’re planning to conduct a source test for compliance purposes (e.g., when it’s required by a permit condition), be sure to select a method that is accepted by the regulatory agency requesting the test.
On a side note, if you’re conducting an engineering test (a test not being used for compliance purposes), the method you use won’t matter. But because most engineering tests are done to collect data on how equipment behaves during a compliance-related test, it’s best to use methods that are the same as or similar to agency-accepted testing methods.
2. Certified contractors are sometimes needed to conduct a source test.
Depending on how you plan to use the test results, you may need to retain a contractor who is certified by the regulatory agency for which you are conducting the test, such as an AQMD Certified Permitting Professional. If a certified contractor is needed (which is often the case, particularly when it comes to compliance-related tests), you can ask the agency for a list of their certified specialists.
Source testing can be complicated, what with all of the variables that exist between methods, sampling equipment, and techniques. Hiring a professional can help simplify some of these complexities, thus bringing peace of mind and possibly even bringing down costs. This isn’t the time to cut corners, because someone who doesn’t know all the ins and outs might introduce errors that produce inaccurate — and, thus, costly — results. Hiring a certified testing consultant can often prove more cost-effective than using in-house staff.
3. Testing protocols may need to be approved prior to conducting a source test.
Sometimes source tests are used to demonstrate compliance to a specific rule or emission limit, while sometimes they’re used as a source of data for a specific piece of equipment, as in the case with engineering tests.
Testing methods are just a subset of overall testing protocol, which can include such additional factors as the length of time of a test, the number of times a test will be conducted, etc. When you’re conducting source testing for a regulatory agency, you will most likely need to submit a source-test protocol for approval prior to conducting the test, to ensure that everyone (i.e., your staff and the agency) involved is on the same page.
4. Source-test results may not imply actual emissions.
This point is counterintuitive, but it is important nonetheless. Generally speaking, emissions are dependent on the load that is placed on a particular piece of equipment when it is in operation.
Common metrics for measuring a load include amount of materials being processed, types of material being processed, and fuel-flow rate for a burner/engine, to name just a few.
Given all these factors, it’s important to consider the load at which you want to collect your data. In other words, do you want to measure emissions at an average or at a maximum load?
In most cases where a test is needed to demonstrate compliance with a rule, test results must be collected at the maximum end of the equipment’s normal operating range, because the agency is looking for the maximum possible emissions.
For example, if the fuel-flow rates for a piece of equipment range from 500 to 1,500 standard cubic feet per hour (SCFH) during normal operation, then the test should be conducted when the equipment is operating with a fuel-flow rate that is closest to 1,500 SCFH.
5. Be sure that the emissions from the process do not interfere with the source test.
Depending on the configuration of your process and piece of equipment, you’ll need to consider the emissions from your process when planning for your source test.
For common pieces of equipment such as a boiler or engine, conducting a source test requires measuring the emissions at the exhaust stack of the equipment. In such cases, the process that the boiler or engine is serving won’t typically interfere with the emissions found in the exhaust stack since these emissions are the direct result of the combustion of a fuel.
But that’s not always the case. For example, if you measure the emissions of oxides of nitrogen (NOx) from a coffee roaster operation, you’ll be measuring emissions from both the beans and the burner. Depending on the situation, you may only need to measure the emissions from the burner. (To determine if your situation falls under these guidelines, you may have to get clarification from the agency — or use your engineering knowledge.) If so, you’ll need to develop a way to operate the roaster without beans in the equipment.
A similar situation arises when you need to measure emissions from equipment such as a clay kiln or crematorium: Do you perform the test with the product (coffee beans, tiles, human remains, etc.), or without?
If you have questions about completing a source test, contact us and we can get you pointed in the right direction.