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This guidance is for:Ìý

• 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.Ìý

1. OverviewÌý

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

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.Ìý

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.Ìý

 are a certification body appointed to run this scheme for us.Ìý

You can find the requirements for certification and for the manufacturer’s quality management system for manufacturing and design control of monitoring systems in:Ìý

• EN 15267-1 Air quality – Certification of automated measuring systems – Part 1: General aspectsÌý
• EN 15267-2 Air quality – Certification of automated measuring systems – Part 2: Minimum requirements for product quality assurance, initial assessment, and on-going surveillanceÌý

2. IntroductionÌý

This standard specifies performance criteria for CO₂-LTS. These consist of:Ìý

• general criteria for all automated measuring systemsÌý
• performance criteria and test procedures for testing in a laboratoryÌýÌý
• performance criteria and test procedures for field testingÌý

3. Required standards for CO₂-LTSÌýÌý

You will need the following standards for the testing of CO₂-LTS under MCERTS:Ìý

• 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 requirementsÌý

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.Ìý

4.1 Application of performance requirementsÌý

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.ÌýÌý

4.2 Ranges to be testedÌý

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

4.3 Certification rangesÌý

No certification range is required for biogenic CO₂ ratio.ÌýÌý

4.4 Manufacturing consistency and changes to CO₂-LTS designÌýÌý

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.ÌýÌý

4.5 Qualification of test laboratoriesÌýÌý

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.Ìý

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

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.Ìý

5.1 CO₂-LTS for testingÌýÌý

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.ÌýÌý

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.ÌýÌý

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.ÌýÌý

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

5.2 Evidence of compliance of legal requirementsÌýÌý

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.Ìý

5.3 SecurityÌýÌý

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

5.4 Operational status signalsÌýÌý

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

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

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

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

5.5 Degree of protection provided by enclosureÌýÌý

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).ÌýÌý

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.ÌýÌý

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.Ìý

5.6 Influence of ambient temperatureÌýÌý

The manufacturer shall make sure that the CO₂-LTS is capable of operation from:ÌýÌý

• -20°°ä to +50°C for assemblies installed outdoorsÌýÌý
• +5°°ä to +40°C for assemblies installed indoors, where the temperatures do not fall below +5°°ä or rise above +40°CÌýÌý

5.7 Influence of supply voltage variationsÌýÌý

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

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

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

6.1 CO₂-LTS performance criteria for laboratory testingÌý

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.Ìý

Table 1: CO₂-LTS performance criteriaÌý

Performance characteristic	Performance criteria
Minimum operational velocity range for proportional sampling	2 to 30 m/s
Accuracy of proportional sampling over measurement range	25% of the sample volume
Response time (T90) volume proportional response to change in velocity	<100s

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.ÌýÌý

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.Ìý

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.Ìý

6.2 Operational velocity range for proportional samplingÌýÌý

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

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

6.3 Storage capability of CO₂ absorberÌýÌý

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.Ìý

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.ÌýÌý

6.4 Losses of collected substanceÌýÌý

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.Ìý

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

6.5 CO₂ absorber labellingÌýÌý

The measuring filters, cartridges or absorption tubes shall be clearly marked (for example by hand or by stamp) with:ÌýÌý

• measurement site identificationÌýÌý
• date and sample timesÌý
• sample numberÌýÌý
• sampling durationÌýÌý

• volume of extracted gasÌýÌý

• mass of adsorber cartridge before and after the samplingÌý

6.6 Essential characteristic documentationÌýÌý

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.Ìý

6.7 Adaptable to plant operation conditionsÌýÌý

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

7. Field testing performance criteria and test proceduresÌý

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.Ìý

7.1 CO₂-LTS performance criteria to be field testedÌý

Table 2: Performance criteria for the field testÌý

Performance characteristic	Performance criteria
Maintenance interval	>1 month
Availability during field test	>90%
Reproducibility	<3% modern carbon (MC)
Verification with reference method	±3% MC
Contamination check	No visible salts in sample tubes

7.2 Requirements for the field testÌý

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.Ìý

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.ÌýÌý

The sample location shall be in accordance with EN 15259.Ìý

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

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.Ìý

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

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.Ìý

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

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

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.Ìý

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.ÌýÌý

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.Ìý

7.3 Verification of the CO₂-LTS against a reference methodÌýÌý

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

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.ÌýÌý

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

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.ÌýÌý

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.Ìý

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.Ìý

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.Ìý

7.4 ReproducibilityÌý

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

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.ÌýÌý

R_D shall be calculated according to the following formula:Ìý

R_D = upper limit of the measuring range divided by S_D.t_f;0.95

Where:Ìý

• S_D is the standard deviation of differences between parallel measurementsÌý
• t_f;0.95 is the Student’s t-factor; statistical confidence level 95%Ìý

Table 3: Student’s t-factorsÌý

Number of parallel measurements (n)	tf;0.95 (n-1)
3	2,920
4	2,353
5	2,132
6	2,015
7	1,943
8	1,895
9	1,860
10	1,833
11	1,812
12	1,796
13	1,782
14	1,771
15	1,761
16	1,753
17	1,746
18	1,740
19	1,734
20	1,729
25	1,711
30	1,699

7.5 AvailabilityÌý

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

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.Ìý

The availability shall be determined from the following formula:Ìý

V = ((t_tot – t_o) divided by t_tot) 100Ìý

Where:Ìý

• V is the availability of CO₂-LTS (percent)
• t_tot is the total operating timeÌý
• t_o is the total outage of CO₂-LTSÌý

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.ÌýÌý

The results shall be summarised in tabular form.Ìý

7.6 BreakthroughÌý

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

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.ÌýÌý

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.Ìý

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

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.Ìý

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.ÌýÌý

Do notÌýcalculate 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.ÌýÌý

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.Ìý

7.7 Contamination checkÌýÌý

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.Ìý

7.8 Maintenance intervalÌý

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

8. What to do nextÌý

Find out more about MCERTS product certification on the:Ìý

• Ìý
• MCERTS collection on ÒÁÈËÖ±²¥Ìý

Contact the Environment Agency if you need any help.