Test Port Guidelines
"Where do I install the Test Ports?"
One question that we are frequently asked is, “Where exactly do I need to install test ports?” Test port locations are discussed in detail in EPA Method 1 (and 1A for small ducts). You can contact us and we will be happy to discuss the test port locations for your particular process.
For a standard round duct greater than 12 inches in diameter, the general rule of thumb is that you need to have a straight section of duct upstream of the test ports equal to at least two duct diameters and a straight section of duct downstream of the test ports equal to at least a half duct diameter. From the test ports, upstream will be toward the process and downstream will be toward to exhaust point. Each section of straight duct should be free of any disturbance (i.e. duct transitions, straightening vanes, dampers, etc.)
Due to the language used in EPA Method 1, many people often misinterpret the minimum requirements to be eight diameters upstream and two diameters downstream for test ports. Although this is the preferred criteria, EPA Method 1 states an alternate minimum criteria of two diameters upstream and a half diameter downstream for test ports. This alternate criteria is perfectly acceptable for most ducts. The only impact of using less than the eight diameters upstream and two diameters downstream criteria is that the number of traverse points used during the sampling will be increased. Instead of sampling at twelve different points in the duct during a test run, the air testing team may have to sample at up to twenty-four different points.