What is a POC?

• POC stands for Parameter Occurrence Code.
• POC is a convenient method for tracking multiple measurements of a single parameter at one site.
• Each additional instrument that measures a specific pollutant at a monitoring site is assigned a new POC.
• For example, the first Ozone monitor at a site will generally have a POC of 1. If a second Ozone monitor is installed, it will generally have a POC of 2.
• The TREX may have also assigned a new POC to distinguish a change in reporting organization or a major method change.
• The following is extracted from the EPA manual on coding:
POC is a code used to distinguish between different monitors at one site that are measuring a parameter. For example, the first monitor established to measure CO at a site would have POC = "1". If an additional monitor were established at the same site to measure CO, that monitor would have POC = "2". However, if a new instrument were installed to replace the original instrument used as the first monitor, that would be the same monitor and it would have POC = "1". For criteria pollutants, data from different sampling methods should only be stored under the same POC if the sampling intervals are the same and the methods or references are equivalent. For sites where duplicate sampling is being conducted by multiple agencies or one agency with multiple samplers, multiple POC's must be utilized to store all samples. For non-criteria pollutants, data from multiple sampling methods can be stored under the same POC if the sampling intervals are the same.