4 The record articles

Reflections from 2018 Year End Reporting – Part 2: Ancillary Analyzer Impacts on Data Validity

Posted: February 21st, 2019

Authors: Matt C. 

Welcome to the second of a five-part blog series hosted by ALL4’s Continuous Monitoring Systems (CMS) Practice Area. If you missed Part 1, be sure to check it out here.  In Part 2, we review how ancillary analyzers can affect continuous monitoring system’s (CMS) data validity.  Examples of ancillary analyzers include volumetric flow monitors, diluent analyzers such as oxygen (O2) or carbon dioxide (CO2), and fuel flowmeters.

Provided herein is an example of how a volumetric flow monitor can impact data across several CMS, and it is important to note that this example is not only applicable to volumetric flow monitors, but to any ancillary analyzer.  Volumetric flow monitors are a common component to many CMS.  Whether it is a carbon monoxide (CO), nitrogen oxide (NOX), or sulfur dioxide (SO2) continuous emissions monitoring systems (CEMS), volumetric flow monitors are often used to convert pollutant concentrations to units of mass.  Therefore, the “health” (i.e., valid or invalid status) of the volumetric flow data is equally important as the CO, NOX, or SO2 concentration data for mass rate CEMS.  An emission source typically has one volumetric flow monitor that can serve multiple mass rate CEMS.  Thus, the ongoing quality assurance (QA) validations (sometimes referred to as “calibrations”) for a single volumetric flow monitor can impact multiple CMS.

In this past quarterly and semi-annual reporting period at ALL4, we saw the volumetric flow monitor validations affect data in the two different scenarios outlined below.

  1. The volumetric flow analyzer failed a daily validation which caused invalid and out-of-control (OOC) volumetric flow data, thus invalidating the CO, NOX, and SO2 mass emission rate data from the last successful validation until a validation (or actual calibration) was passed the following day.
  1. The volumetric flow analyzer’s validations exceeded the maintenance limit for five consecutive days unnoticed by the facility. On the fifth day that the maintenance limit was exceeded, volumetric flow data (and thus CO, NOX, and SO2 mass emission rate data) became invalid from the time the maintenance limit was exceeded until a passing (below the maintenance limit) validation (or actual calibration) was completed days later.  Note that this example is specific to CEMS required to comply with the QA procedures of 40 CFR Part 60, Appendix F.

The take-away here is that ancillary analyzers are often relied upon by many CMS at a facility, and therefore, the health of the data collected by the ancillary analyzers is critically important to those CMS.  Failing ongoing daily validations, or exceeding maintenance limits on consecutive days, is an easy way to quickly accrue multiple hours of invalid and OOC ancillary analyzer data that impacts multiple CMS.

If you have any questions about a volumetric flow monitor’s impact on data, or any other general CMS questions, please reach out to me.  I can be reached at 610.933.5246 extension 139, or at mcarideo@all4inc.com.

Don’t forget to read Part 3: Temperature Monitoring and Impacts on Data Validity of this five-part blog series on how temperature monitoring system data affects (or doesn’t affect) CMS data validity!  To ensure that you do not miss out on the action, signup for our 4 The Record subscription below to receive these articles directly in your inbox.


    Sign up to receive 4 THE RECORD articles here. You'll get timely articles on current environmental, health, and safety regulatory topics as well as updates on webinars and training events.
    First Name: *
    Last Name: *
    Location: *
    Email: *