Location of Sample probe for Continuous Emission Monitoring Systems (CEMS)


Thread Starter


Dear All

I need to know the location of probe in Chimney. Is there any International Standard which tells where the sample probe for So2, NOx, O2 analyser is to be mounted?

Is there any thumb rule or standard which tells how to calculate the location of probe give the chimney diamer and height.

Also I need to know does the location of sample probe depend on the material of construction of chimney like Concrete or Steel. In other words, does it vary if the chimney is made of steel or concrete?

Who is supposed to tell about the location of sample probe? Is it the C&I design engineer or process design engineer or Structural / civil design engineer?

Also comes under which standard? mechanical or civil /structural or C&I standard?



anand s

Richard O'Donnell


you seem to be asking about two (2) separate topics... I really cannot answer thoroughly in this posting however, here is a basic "starting point" for you. Email me and can provide some documents for you:

In a pipe, you want to sample at a location where laminar flow is present, this is determined by a general "rule of thumb" method by taking the Diameter (id) of the pipe and then multiplying it by (i believe) 5 or 6, the object is to be "so many pipe diameters" down stream of any source of turbulent (non-laminar) flow (i.e., elbow, valve, etc.)

A PIDOT tube is a good Delta-p type of flow measuring transducer to place at sample location.

For stacks, the typical methods are US EPA METHODS 5, AND 23, SURF TO EPA SITE AND YOU WILL LINK TO MORE STANDARD METHODS THAN YOU WILL EVER NEED. Also, you can use ASTM methods.

Regards, Rick