MCERTS: performance standard for long-term samplers of carbon dioxide
Source: gov.uk (2025-07-25)

For manufacturers of long-term samplers and test laboratories who carry out testing of equipment.

This guidance is for:
- manufacturers of long-term samplers (LTS) for the determination of biogenic carbon dioxide (CO2) emissions, who need to know what standards to meet to be able to sell their equipment in the UK
- test laboratories who carry out testing of equipment on behalf of manufacturers to see if it meets the required standard
We set up our monitoring certification scheme (MCERTS) to provide guidelines on the standards you need to meet to monitor emissions that affect the environment.

1. Overview

Here we describe the certification process for LTS for the determination of biogenic CO2 (CO2-LTS) emissions.

These systems measure the CO2 in industrial chimney stacks. They extract a sample of CO2 for analysis at a laboratory. This standard applies to the certification of the CO2-LTS only. It is not applicable to the transport, storage, analysis, and reporting of results.

MCERTS for CO2-LTS is an official certification scheme that complies with EN ISO/IEC 17065 Conformity assessment – Requirements for bodies certifying products, processes, and services.

CSA Group UK Ltd (https://www.csagroupuk.org/services/mcerts/mcerts-product-certification/) are a certification body appointed to run this scheme for us.

You can find the requirements for certification and for the manufacturer’s quality management system for manufacturing and design control of monitoring systems in:
- EN 15267-1 Air quality – Certification of automated measuring systems – Part 1: General aspects
- EN 15267-2 Air quality – Certification of automated measuring systems – Part 2: Minimum requirements for product quality assurance, initial assessment, and on-going surveillance
2. Introduction

This standard specifies performance criteria for CO2-LTS. These consist of:
- general criteria for all automated measuring systems
- performance criteria and test procedures for testing in a laboratory
- performance criteria and test procedures for field testing
3. Required standards for CO2-LTS

You will need the following standards for the testing of CO2-LTS under MCERTS:
- EN ISO 13833 Stationary source emissions – Determination of the ratio of biomass (biogenic) and fossil-derived carbon dioxide – Radiocarbon sampling and determination
- EN 15267-3 Air quality – Certification of automated measuring systems – Part 3: Performance criteria and test procedures for automated measuring systems for monitoring emissions from stationary sources
- EN 15259 Air Quality – Measurement of stationary source emissions – Requirements for measurement sections and sites and for the measurement objective, plan, and report
4. General requirements

Here we describe the general requirements from EN 15267-3 that are applicable to the certification of CO2-LTS. We provide additional requirements that are specific to CO2-LTS later in this document.

4.1 Application of performance requirements

The test laboratory shall test at least 2 identical CO2-LTS. All CO2-LTS tested shall meet the performance criteria specified in this document as well as the requirement for the maximum permissible expanded uncertainty.

4.2 Ranges to be tested

For velocity range a minimum of 2 to 30 metres per second (m/s) shall be used.

4.3 Certification ranges

No certification range is required for biogenic CO2 ratio.

4.4 Manufacturing consistency and changes to CO2-LTS design

Certification is specific to the CO2-LTS version, that has undergone performance testing. Subsequent design modifications that might affect the performance of the CO2-LTS may invalidate the certification.

4.5 Qualification of test laboratories

Test laboratories shall have the competence for performing emission measurements and carrying out the tests defined in this document. Test laboratories shall have the knowledge on the uncertainties attributed to the individual test procedures applied during the performance test.

5. Performance criteria and test procedures for laboratory testing of CO2-LTS

Here we describe the general performance criteria from EN 15267-3 for laboratory testing that are applicable to CO2-LTS. The test laboratory shall make sure that CO2-LTS meet the criteria using the test procedures provided in EN 15267-3.

5.1 CO2-LTS for testing

All CO2-LTS for testing shall be complete, including the operation manual. The performance criteria apply to the complete CO2-LTS and not to the individual parts. The test report shall be issued for the specific CO2-LTS with all the main components.

CO2-LTS shall have appropriate provisions for filtering solids and effective control of water condensate, where applicable. The CO2-LTS shall be designed to prevent chemical reactions within the sampling system and washout of CO2 in water condensate, where applicable.

CO2-LTS with different options for the sampling line length shall be tested with an appropriate sampling line length agreed between the test laboratory and the manufacturer. The length shall be quoted in the test report.

The test laboratory shall describe in the test report the type of sampling system.

5.2 Evidence of compliance of legal requirements

CO2-LTS manufacturers shall supply verifiable and traceable evidence of compliance with the requirements of the relevant product marking requirements for the intended market. This includes requirements on electromagnetic compatibility and voltage limits.

5.3 Security

The manufacturer shall make sure that the CO2-LTS shall have a means of protection against unauthorised access to control functions.

5.4 Operational status signals

Manufacturers shall make sure that CO2-LTS have a means of displaying their operational status.

The sampling system shall be able to process status information about the operation of the plants.

Status signal covers normal operation, stand by, maintenance mode and malfunction error signals.

The CO2-LTS shall have a means of communicating the operational status to the plants control system.

5.5 Degree of protection provided by enclosure

Equipment protected from rain (that is they are in ventilated rooms or cabinets) shall meet at least IP40 as specified in EN 60529 Degrees of protection provided by enclosures (IP codes).

Equipment located where some kind of shelter against precipitation is in place (for example a porch roof) but where rain can reach, shall meet at least IP54 as specified in EN 60529.

Equipment designed for outdoor use in the open air and without weather protection shall at least meet the requirements of standard IP65 as specified in EN 60529.

5.6 Influence of ambient temperature

The manufacturer shall make sure that the CO2-LTS is capable of operation from:
- -20°C to +50°C for assemblies installed outdoors
- +5°C to +40°C for assemblies installed indoors, where the temperatures do not fall below +5°C or rise above +40°C
5.7 Influence of supply voltage variations

The manufacturer shall make sure the CO2-LTS can operate at a supply voltage of -15% and +10%.

6. Performance criteria and laboratory test procedures specific to CO2-LTS

Here we describe the performance criteria and laboratory test procedures that are specific to CO2-LTS.

6.1 CO2-LTS performance criteria for laboratory testing

In the velocity range 2 to 30 m/s the CO2-LTS shall sample a portion of the stack gas into a cartridge. The portion sampled shall be dependent on the measured stack gas velocity or volume flow. The CO2-LTS shall have the capability to adjust the sample volume, depending on the stack gas velocity.

Table 1: CO2-LTS performance criteria

The minimum operating velocity, below which the equipment fails to measure and respond flow proportionally, shall be determined by increasing the velocity of the sample, using a wind tunnel. The velocity shall be increased from zero until the equipment responds with a performance criterion of less than 10%. This minimum value shall be verified by reducing the velocity of the sample from a higher velocity to the minimum value to make sure the equipment continues to respond correctly.

The accuracy of proportional sampling at different gas velocities shall be assessed using a wind tunnel. The measurement shall be made using a reference instrument whose calibration is traceable to national standards. This shall be assessed in the range of 2 to 30 m/s.

The response time shall be measured by introducing randomised step changes in the velocity at the input to the CO2-LTS. The size of each step shall be between 10 and 95% of the operational velocity range. The random sequence of steps shall include both increased and decreased velocities and need not start from or end at zero.

6.2 Operational velocity range for proportional sampling

In the laboratory test, velocities at 20, 50 and 80% of the range of velocities shall be simulated.

The proportional sampling shall have a maximum uncertainty of 25% of the required sample volume.

6.3 Storage capability of CO2 absorber

The storage capability of the CO2 absorbing media used for sampling shall be determined in the context of performance testing and assessed in relation to the measurement objective.

Where a breakthrough CO2 sensor is not used, the storage capability of the media used for sampling shall be 125% of the maximum CO2 sampled.

6.4 Losses of collected substance

Losses of measured CO2 in the sample gas line (for example, removed with condensate) shall not exceed 5% of the CO2 sampled in the cartridge. This shall be checked by measuring the CO2 concentration before the absorber or in the condensate.

If a CO2 sensor is used before the absorber, the range of the sensor shall be 0 to 20% volume concentration (volume fraction).

6.5 CO2 absorber labelling

The measuring filters, cartridges or absorption tubes shall be clearly marked (for example by hand or by stamp) with:
- measurement site identification
- date and sample times
- sample number
- sampling duration
volume of extracted gas
- mass of adsorber cartridge before and after the sampling
6.6 Essential characteristic documentation

Essential characteristic data shall be automatically documented in a printer log (for example, the effective sampling period and total period of use). Electronic data carriers may also be used.

6.7 Adaptable to plant operation conditions

The start time and duration of sampling and pause intervals shall be adjustable and adaptable to the operating conditions of the plant.

7. Field testing performance criteria and test procedures

Here we describe the performance criteria and field test procedures of CO2-LTS installed at an industrial plant. Where applicable, the performance criteria and test procedures in EN 15267-3 shall be followed.

7.1 CO2-LTS performance criteria to be field tested

Table 2: Performance criteria for the field test

7.2 Requirements for the field test

Field tests shall be performed to validate the sampling efficiency of CO2-LTS across a period consistent with its specification and its specified maintenance interval.

Field tests shall be carried out at a suitable industrial process, preferably a municipal waste incinerator with percentage MC levels between 50 and 70% MC.

The sample location shall be in accordance with EN 15259.

The system shall be assembled and set-up according to the manufacturer’s installation instructions.

Sampling shall be done at a representative position in the stack. The measurement for identifying the representative sampling point shall be performed during normal plant operating conditions.

To confirm the selected sampling point and the proper configuration of the CO2-LTS, preliminary comparison measurements with the reference method shall be performed.

The CO2-LTS shall be configured so that at each service a leak test can be done on the mainstream parts. This leak test shall make sure that less than 5% leakage occurs at the normal flow rate. The leak test shall be done by applying a vacuum.

During sampling, the sampling flow shall be checked every 30 minutes over the total sampling period.

Sample traps shall be sealed during transport and when not in use.

If a cartridge is used it shall be tested in the laboratory for leaks, to enable a storage time of at least 3 months. This can be done be weighing the cartridge, storing it, and then reweighing it.

A sufficient sample mass shall be collected during all tests of the field test so that the quantification limit of the analysis is met. These are 2g for analysis with accelerator mass spectrometry and 7 to 8g for analysis with liquid scintillation.

Where a breakthrough sensor is not installed, the CO2 absorber capacity left after sampling shall be more than 25% of the total capacity of the absorber.

7.3 Verification of the CO2-LTS against a reference method

Field tests shall be carried out to demonstrate the verification of the CO2-LTS against the reference method EN ISO 13833.

The sampling points of the reference method and both the CO2-LTS shall be as close as possible to each other. They must not cause interference to the flow conditions at their respective sample locations.

The verification of the CO2-LTS against a reference method shall be determined by parallel measurements carried out using EN ISO 13833.

Test laboratories shall have the competence to perform reference method measurements. Having EN ISO 13833 on their EN ISO 17025 schedule of accreditation can demonstrate this. If a test laboratory with accreditation for sampling using EN 13833 is not available, then a test laboratory that has accreditation for EN 1948-1, EN 13211 or EN 14385 is acceptable.

The CO2-LTS and reference method sampling shall be performed in parallel for a specified time. The time shall be at least 40 hours. The CO2-LTS and reference method are performed simultaneously. The sampling unit of the reference method is exchanged to produce multiple samples whereas the sampling unit for the CO2-LTS is kept for the specified time. This results in one sample for the CO2-LTS and a mean value of at least 5 samples for the reference method.

The difference between the mean value of the multiple samples of the reference method and the single CO2-LTS sample shall be within ±3% MC of the value determined by the reference method.

Note: ±3% MC is the measurement uncertainty specified in ASTM D6866 Standard test methods for determining the biobased content of solid, liquid and gaseous samples using radiocarbon analysis.

7.4 Reproducibility

Reproducibility (RD) shall be determined during the field test from simultaneous measurements by means of identical CO2-LTS at the same measurement point (paired measurements).

Field tests shall be carried out at a suitable industrial process, preferable a municipal waste incinerator with percentage MC levels between 50 and 70% MC.

RD shall be calculated according to the following formula:

RD = upper limit of the measuring range divided by SD.tf;0.95

Where:
- SD is the standard deviation of differences between parallel measurements
- tf;0.95 is the Student’s t-factor; statistical confidence level 95%
Table 3: Student’s t-factors

7.5 Availability

During the field test the availability of the sampling system shall be at least 90%.

The test laboratory shall determine the availability of the CO2-LTS by recording the duration of the field test and all interruptions to the normal functioning of the CO2-LTS. Interruptions include malfunction, servicing, zero and span point checks.

The availability shall be determined from the following formula:

V = ((ttot – to) divided by ttot) 100

Where:
- V is the availability of CO2-LTS (percent)
- ttot is the total operating time
- to is the total outage of CO2-LTS
The outage time includes all interruptions to the normal functioning of the CO2-LTS, such as malfunctions, servicing, maintenance, leak checks and sample medium exchange. A malfunction of the CO2-LTS is when it stops sampling because of an error, such as the pump fails, or a volume flow measurement error occurs.

The results shall be summarised in tabular form.

7.6 Breakthrough

Breakthrough shall be less than 5% from 0 to 100% use of the absorbent material and the maximum sampling velocity.

Breakthrough can be determined in an analytical laboratory using 1, 2 or more layers of sorption material or by using a CO2 sensor installed after the cartridge.

If the CO2-LTS uses CO2 measurement to detect breakthrough this sensor shall be included in the testing. The CO2 sensor shall be installed after the absorber cartridge. The detection limit of the sensor shall be less than 100 ppm.

The range of the sensor shall be 0 to 2,000 parts per million (ppm).

Span and zero gas shall be used to check ongoing performance of the sensor. Criteria from CEN/TS 17405 Determination of the volume concentration of carbon dioxide shall be used.

Determine breakthrough by multiplying the CO2 mass concentration by the sample volume to give a CO2 mass. If the sampled CO2 mass reaches 75% of the calculated maximum adsorber capacity, the sampling should be stopped.

Do not calculate the sampled CO2 mass using an estimated CO2 concentration. The CO2 concentration can be measured in the stack using a continuous emissions monitoring system. It can also be measured by a sensor installed before the CO2 absorber cartridge.

You can also determine breakthrough by using a CO2 sensor installed after the absorber cartridge. The sampling shall be stopped if the breakthrough sensor exceeds 1,000 ppm.

7.7 Contamination check

The response of the CO2-LTS to soiling shall be determined in the field test by means of visual checks. At the end of the test the effect of the contamination shall be evaluated.

7.8 Maintenance interval

The minimum maintenance interval of the CO2-LTS shall be at least 1 month.

8. What to do next

Find out more about MCERTS product certification on the:
- CSA website (https://www.csagroup.org/en-gb/services/mcerts/mcerts-product-certification/)
- MCERTS collection on GOV.UK (https://www.gov.uk/government/collections/monitoring-emissions-to-air-land-and-water-mcerts)
Contact the Environment Agency if you need any help.

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