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Tools -  EPA Method 1

(for port location on circular ducts only)


Criteria: Ports must not be located less than 0.5 stack diameters upstream and 2.0 stack diameters downstream from any flow disturbance.



Duct diameter (D):
Input the duct diameter here.
  Minimum Ideal  
Upstream distance (A):
The port is upstream from Disturbance Y
Downstream distance (B):
The port is downstream from Disturbance Z
Equivalent upstream diameter:
Calculation: Distance A/Distance D
Equivalent downstream diameter:
Calculation: Distance B/Distance D

Disturbance: Any bend, expansion, contraction, conversion, connection, or other solid obstruction located within a duct.

Important Notes:

  1. The spreadsheet above can be used to calculate equivalent upstream and downstream stack diameters. Just input the inside stack diameter, making sure not to include ports or obstructions.
  2. This criteria applies to both vertical and horizontal, circular ducts. Verify the direction of the gas flow before calculating upstream and downstream diameters.
  3. Measurements must be taken from the center of the port, and from the upstream and downstream disturbance-points closest to the port.
  4. The best case scenario for port location is at least 2.0 diameters upstream and 8.0 diameters downstream from any flow disturbances.
  5. Ports need to be installed on the same horizontal plane, perpendicular to the direction of the flow.
  6. Ports should have a coupling length of 5-6 inches from the outside stack wall and be 4 inches in diameter. The ports should also be able to support at least 75 pounds. If PM10 measurements are necessary (now or in the future), port diameters should be 6 inches.
  7. Make sure all ports are grinded out and that the couplings do not extent past the inside stack wall.
  8. On vertical stacks, eyelets should be installed directly above each port (approximately 30 inches).