EPA Method 1 – Options for Sample Port Installation

Too often the installation of sampling/testing ports is an afterthought in the process of stack construction.  However, sampling ports are essential to the stack testing process which is a requirement for demonstrating compliance.  In fact, the EPA goes so far as to state outright that Method 1 should be taken into consideration before stack construction begins.

Having a better understanding of EPA Method 1 can reduce or eliminate the need for excess modifications on an existing source.  That means knowing the optimum location for sampling ports can save money in your compliance testing budget.

So what is EPA Method 1 exactly and how can it be helpful to the pre-construction design and post-construction installation of sampling ports?

Simply stated, EPA Method 1 is a way to determine sampling port locations that are free from swirling air, or cyclonic flow.

What causes Cyclonic Flow?

Cyclonic Flow occurs when the sampling plane is too close to a disturbance (vane straighteners, fans, control equipment, etc.) or any duct configuration that causes a disturbance in the air flow causing the air to swirl rather than travel on a linear path.

Determining Placement of Sampling Ports

EPA Method 1 provides two options for sample port installation, as follows:

Simplified – Used most often and applies to most stacks

Alternative – Used for smaller stacks with a diameter less than 12 inches

The majority of our clients have larger stacks, so we’ll overview the Simplified Port Installation guidelines, but don’t hesitate to call us at 1-888-363-0039 if you need assistance understanding Alternative Port Installation.

Three Conditions for Simplified Port Installation

  1. The flow through the stack at the port location must be non-cyclonic.

Following Method 1 procedures as detailed by the EPA prevents issues with cyclonic flow for most stationary sources.  Cyclonic flow at a sampling plane will skew results which becomes an expensive issue if it causes compliance failure, that’s why ESS conducts EPA Method 1 with all stack testing.

  1. The stack diameter must be 12 inches or greater or 113 square inches in a cross-sectional area.

When the stack diameter is less than 12 inches, Alternative Port Installation must be used.

  1. The sampling plane must be located more than two stack diameters downstream from the nearest upstream disturbance  and more than half a stack diameter upstream from the stack exit or next downstream disturbance.  (See Diagram 1).
Diagram 1 Determining Sampling Plane

Diagram 1 Determining Sampling Plane

disturbance is anything that interrupts or alters the flow of air and gas through the stack.  Examples of disturbances include: fans, duct bends, stack exits and vane straighteners.

Upstream measurement is the distance between the test ports and the nearest upstream disturbance.

Conversely, downstream measurement is the distance between the test ports and the stack exit.

To calculate the equivalent diameter of a rectangular duct use the equation:
De= 2(LxW) / (L+W)

While those three items cover the requirements for Method 1 Simplified Port Installation, there are still other sampling port factors to consider for a smooth test day.

Port Size and Pollutants Tested

Particulate, metals, dioxin/furans, flowrate or other manual method tests require a minimum of two (2) 4”-diameter ports located 90 degrees from each other.  PM10 and PM2.5 require at least two (2) 6”-inch ports.  It is common to install four (4) of these test ports 90 degrees apart from each other so that more testing can be conducted simultaneously.

Sampling ports for gases should be greater than one-quarter-inches in diameter and installed directly above one of the manual method ports.

Port Access

OSHA-compliant platforms are required for the testing team to access the sampling plane safely and effectively.  If a temporary platform must be erected, then OSHA-compliant scaffolding is preferred, but man lifts are also acceptable.  Scaffolding should be constructed directly in front of each sample port with enough room for the sampling equipment to access the ports (see diagram 2).

Diagram 2 Scaffolding Placement

Diagram 2 Scaffolding Placement

The safety of our crew is of utmost concern, so OSHA-compliant structures are mandatory for testing.

When test day arrives, be sure that sample ports are clean and free from debris.  Sample port condition is regularly monitored by state regulators.

Stack pressure and stack temperature can also affect sampling plane design—call us if you have questions on this point.

There are many issues to consider for an emissions test.  Being prepared with the knowledge to properly construct sample ports will save money by preventing excessive stack modification.  Furthermore, understanding and adhering to the guidelines of EPA Method 1 will ensure that sample port, size, placement, and access are not an issue on test day.

For assistance in determining your specific sampling port needs, questions about EPA Method 1, or any other stack testing issues feel free to call Environmental Source Samplers at 1-888-363-0039.  It would be our pleasure to assist you.

Download a PDF version of this article.

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