Port Placement for Stacks >12" in Diameter

Port Placement Diagram

It is very important that sample ports be available on the day of the source test. Most air districts will not accept sampling over the top of a stack, as such measurements may not be representative of pollution emissions or total volumetric flow rate from an emission source. If sample ports already exist, please check on their condition to see if they can be opened easily. A welding torch may be required to loosen ports that have excessive rust.

Sample ports should be installed in accordance to EPA Method 1, which is summarized below:

The table below calculates the placement of ports as a fraction of the rectangular stack width.

Number of PortsPort 1Port 2Port 3Port 4Port 5Port 6Port 7Port 8
21/43/4      
31/63/65/6     
41/83/85/87/8    
51/103/105/107/109/10   
61/123/125/127/129/1211/12  
71/143/145/147/149/1411/1413/14 
81/163/165/167/169/1611/1613/1615/16
Updated 22 November 2011.

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