Navigating New CEMS Regulations: Picarro's Solution for PS-19 Compliance Challenges for Commercial Sterilizers

This paper examines the regulatory framework underpinning the recent changes in the Commercial Sterilizer NESHAP (40 CFR 63 Subpart O). It will delve into the rationale behind the continuous emissions monitoring requirements established by the US EPA, along with detailing those requirements themselves.

United States Environmental Protection Agency logo visible on display screen.

Image Credit:

Many within the sterilization industry are concerned about fulfilling these requirements, given previous technologies' challenges when attempting to demonstrate the requisite responsiveness for compliance. This article will discuss Performance Specification 19 (PS-19), which outlines the framework for facility certification of its Continuous Emissions Monitoring System (CEMS). Subsequently, the paper will explore the post-certification procedures and the methods by which a facility can ensure ongoing compliance if subject to 40 CFR 63 Subpart O.

As it navigates the mandatory components of CEMS compliance, the paper will address how Picarro, Inc. can streamline the process of meeting federal regulations.

Regulatory Landscape

The Clean Air Act (CAA) is the United States’ principal federal legislation concerning air quality and encompasses a wide array of topics pertinent to air quality.

The US EPA has been charged with executing the mandates of this law and has instituted numerous regulatory programs for this purpose. Among these, two are particularly relevant to Performance Specification 19 (PS-19): the National Emission Standards for Hazardous Air Pollutants (NESHAP) [40 CFR Part 63] and the New Source Performance Standards (NSPS) [40 CFR Part 60].

In brief, NSPS established the foundation for emissions monitoring and is primarily recognized for its regulations regarding criteria pollutants, while NESHAP focuses primarily on hazardous air pollutants, such as ethylene oxide (EtO).

Throughout much of the United States, the EPA assigns administrative duties from the CAA to the relevant state and tribal authorities. The EPA retains the role of conducting research and providing technical assistance to the states. While fundamental requirements must be upheld, variations in how states manage these responsibilities result in diverse experiences for the regulated community, contingent upon jurisdiction.

PS-19 is outlined in Appendix B to Part 60, detailing the necessary steps for installing and certifying a CEMS. Quality Assurance Procedure 7 is found in Part 60, Appendix F, offering guidelines for upholding CEMS compliance post-certification.

What is PS-19?

PS-19 can be found in Appendix B of Part 60 and is arguably the most thorough and quality assurance-focused performance specification to date. It comprises six primary tests, as well as stipulation on the use of a time-shared system.

PS-19 begins with prerequisites akin to most CEMS, mandating the utilization of certified reference gases adhering to the “EPA Traceability Protocol for Assay and Certification of Gaseous Calibration Standards.” However, given PS-19’s focus on extremely low-concentration gases, protocol gases can undergo dilution using EPA Method 205 to meet the specified values.

To guarantee accurate measurements and prevent stratification at the CEMS measurement point, installation of the CEMS should occur in a location on the stack/duct that is at least (2.0) equivalent duct diameters downstream of a control device or flow disturbance, and (0.5) equivalent duct diameters from the exhaust or any control device.

PS-19 also requires a way to measure volumetric flow rate and, if the EtO measurements need to be corrected to a dry basis, moisture content. The flow monitor must adhere to the earlier installation criteria, ensuring it is located within (0.5) duct diameters from the CEMS probe.

If moisture correction is necessary, the monitoring system must either integrate a continuous moisture sensor and oxygen analyzer capable of measuring oxygen on both wet and dry bases or be an optical measurement system validated by EPA Method 301.

The CEMS system should be capable of obtaining at least one valid measurement for each measurement point every 15 minutes. This stipulation enables the implementation of time-sharing, wherein multiple measurement points are monitored using a single analyzer.

Upon fulfilling these requirements and ensuring the correct installation, setup, and calibration of the system, the facility can initiate the Performance Specification Test Procedures.

Those tests are briefly summarized below:

Source: Picarro 

Required Test Description Criteria Picarro Demonstrated Performance
1. Interference Test

Section 11.1
Establishes concentration ranges of the background matrix in which the measurement of EtO remains valid. This is typically completed by the manufacturer of the gas analyzer. ≤10 times LOD or ≤ 30 ppbv1  

(Section 13.5)
1.3 ppbv
2. Level of Detection (LOD)

Section 11.2
Determines the smallest
concentration the CEMS
is capable of detecting.
< 20% of applicable limit or action level

(Section 13.1)
0.2 ppbv
3. Response Time Determination

Section 11.3
Determines the amount of time it takes for gas to be transported from the certified calibration cylinders to the probe, and then through the entire system to the analyzer.
For a time-shared CEMS, the sampling time for each measurement point must be 3x the calculated response time, with the overall sample time for each measurement point having to be a 15 minute or less cycle time.
N/A 10 seconds
4. Measurement Error Test

Section 11.4
Determines the CEMS can provide linear responses across the entire range of the instrument. ≤ 5.0% of span or ± 10 ppbv  

(Section 13.3)
5. 7-Day Calibration Drift Test

Section 11.5
A daily Quality Assurance test that establishes that a CEMS measurements remain accurate by checking the system against gas standards on the low end and high end of the instrument. ≤ 5.0% of span or ±10 ppbv for 7-days

(Section 13.2)
6. Relative Accuracy Test Audit (RATA)

Section 11.6
The CEMS is compared to a US EPA reference method conducted by a certified source testing firm. This is to ensure the measurement point captures representative emissions. ≤ 20% of RM2  

(Section 13.4)
< 1% of RM3    


  1. The interference test also permits a passing response if the cumulative interference responses do not exceed 2.5% of the calibration span or ±3.0% of the equivalent EtO concentration used.
  2. If the average RM emission level is lower than 50% of the EtO concentration or emission standard, the emission standard can be employed in the denominator of the RA calculation, and the results must not surpass 15%.
  3. Utilizing OTM-47 for the initial RATA testing.

Maintaining CEMS Compliance

Upon completion of the mandatory quality assurance tests, the facility will submit the results to the relevant administrator for approval of the CEMS certification. Subsequently, the facility must uphold regular preventative maintenance and comply with the stipulations outlined in 40 CFR 60, Appendix F Quality Assurance Procedure 7.

Comprehending these requirements and the essential CEMS maintenance necessary for reliable operation can be challenging for facilities lacking prior experience with such intricate systems.

All CEMS systems feature consumable parts, along with critical components prone to failure if not routinely inspected and serviced. Consequently, 40 CFR Part 63, Subpart A mandates that facilities maintain spare parts and a list to address repair needs promptly.

Every facility must also possess a quality assurance plan, outlining the necessary procedures for a functional CEMS system. This task can be challenging, as even power generation facilities with extensive CEMS experience often rely on specialized consulting firms to create or update these plans.

Recognizing this common necessity among facilities, Picarro has taken the initiative to supply each customer with a site-specific quality assurance plan, encompassing the requisite components and additional details, as part of their purchase.

Commercial sterilizers also have a federal obligation to submit semi-annual compliance reports and quality assurance test reports via the EPA’s Electronic Reporting Tool (ERT).

Procedure 7 Details

Currently, Procedure 7 encompasses the stipulations for sustaining a compliant CEMS. This includes daily calibration drift assessments, quarterly audits, and annual RATA testing.

Daily calibration drift assessments must exhibit results aligning with a predetermined performance specification; failure to meet this requirement will render the CEMS system out-of-control (OOC), leading to the generation of invalid data and potential penalties if corrective action is not taken. Similarly, quarterly audits and annual RATAs are held to specific criteria, and non-compliance with these standards will also classify the system as OOC.

Quarterly audits must be conducted at intervals of no less than 60 days and should not exceed three consecutive quarters without a RATA to maintain compliance. The mandatory quarterly audit can encompass any of the following:

Cylinder Gas Audit (CGA)

  • A CGA entails subjecting the entire CEMS system to a zero gas and two upscale gas concentrations in triplicate succession. According to Section 5.1.3 of Procedure 7, the upscale gases should include a mid-gas (50-60% of span) and a high-gas (80-100% of span).
  • Average results of each triplicate injection must be ≤10% of the span.

Dynamic Spiking Audit (DSA)

  • The DSA bears resemblance to the CGA but involves introducing known standards into the gas stream. In most instances, this necessitates specialized equipment.
  • To pass a DSA, the results shall be either less than 5% of the span value at zero, mid, and high audit points or ≤ 20% of the applicable emission standard.

Relative Accuracy Audit (RAA)

  • An RAA involves a stack test firm visiting the site and performing a condensed RATA. At least 3 runs must be conducted, with the RA calculated in a manner akin to the RATA testing outlined earlier.
  • To successfully complete an RAA, the RA must be ≤ 20% of the Reference Method in the denominator.

In the past, these audits necessitated the facility to engage an additional contractor for their completion and to receive quarterly reports from them.

Procedure 7 also specifies that each facility is subject to Above Span Calibration provisions. If average concentrations over two consecutive hours match or exceed 200% of the instrument's span, the facility must conduct an above span calibration within 24 hours. For many systems, this necessitates regular monitoring of alarm thresholds and concentration averages, along with trained personnel capable of performing the test promptly upon threshold exceedance, even during weekends and holidays.

The RATA must be performed annually, with notification sent to the relevant administrator prior to conducting the test. As mentioned earlier, seeking alternative approval for OTM-47 is advisable, particularly if your facility has consistently shown low-level EtO concentrations, to ensure a more precise audit.

How Picarro Simplifies PS-19 Compliance

Commercial sterilizers are essential to the medical supply chain, ensuring doctors and patients can access lifesaving medical devices.

Picarro empowers sterilizers to focus on the job at hand. With decades of experience, Picarro has the tools and managed services expertise to make compliance with these new CEMS rules easy. The EtO system is seamlessly integrated into any facility, and the Environmental Systems (ESYS) team will assist every step of the way.

With thousands of systems installed and operating on every continent, Picarro has built a reputation for having the most accurate and reliable systems globally.

The systems feature a sturdy Data Acquisition System meticulously configured for seamless reporting to the Electronic Reporting Tool (ERT). Housed in a portable, durable cabinet, they are factory-equipped with automated Above Span Calibration checks, remote Cylinder Gas Audits, and remote access for expert CEMS support.

Environmental experts develop all Quality Assurance documents to adhere to federal regulations and operating permits, and they assist clients with their reporting requirements.

A team of trained field technicians delivers comprehensive preventative maintenance and emergency support. Additionally, annual RATAs are scheduled, and communication with the Administrator regarding why OTM-47 is the optimal choice for conducting the RATA will be facilitated.

The benefits of a Picarro system are vast, but the top three are:

  1. Rapid response times. This allows for timeshare systems, saving overall costs as one analyzer can provide up to three measurement points.
  2. The lowest-in-class detection limit. There is no need to overreport emissions with Picarro solutions, nor is 15 minutes needed to generate a low response. Picarro’s results are generated on two-second averages, meaning users quickly get the best data.
  3. End-to-end emissions monitoring solutions. Picarro takes care of everything, so users can do what they do best – sterilize.


This information has been sourced, reviewed and adapted from materials provided by Picarro.

For more information on this source, please visit Picarro.


Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Picarro. (2024, March 18). Navigating New CEMS Regulations: Picarro's Solution for PS-19 Compliance Challenges for Commercial Sterilizers. AZoCleantech. Retrieved on April 16, 2024 from

  • MLA

    Picarro. "Navigating New CEMS Regulations: Picarro's Solution for PS-19 Compliance Challenges for Commercial Sterilizers". AZoCleantech. 16 April 2024. <>.

  • Chicago

    Picarro. "Navigating New CEMS Regulations: Picarro's Solution for PS-19 Compliance Challenges for Commercial Sterilizers". AZoCleantech. (accessed April 16, 2024).

  • Harvard

    Picarro. 2024. Navigating New CEMS Regulations: Picarro's Solution for PS-19 Compliance Challenges for Commercial Sterilizers. AZoCleantech, viewed 16 April 2024,

Ask A Question

Do you have a question you'd like to ask regarding this article?

Leave your feedback
Your comment type

While we only use edited and approved content for Azthena answers, it may on occasions provide incorrect responses. Please confirm any data provided with the related suppliers or authors. We do not provide medical advice, if you search for medical information you must always consult a medical professional before acting on any information provided.

Your questions, but not your email details will be shared with OpenAI and retained for 30 days in accordance with their privacy principles.

Please do not ask questions that use sensitive or confidential information.

Read the full Terms & Conditions.