Guidance

MCERTS: Performance standard for handheld emissions monitoring systems

Updated 16 January 2026

Applies to England

The Environment Agency set up the monitoring certification scheme (MCERTS) to provide guidelines on the standards you need to meet to monitor emissions that affect the environment.

This guidance is for:

• manufacturers of handheld emissions monitoring systems (HEMS), who need to know what MCERTS standard applies to their equipment
• test laboratories who carry out testing of equipment on behalf of manufacturers to see if it meets the required standard

1. Overview

This section describes the certification process for HEMS.

HEMS make measurements in a wide variety of applications when the user needs a high degree of portability. For example, stack emissions monitoring for indicative purposes, monitoring some plants that fall under the medium combustion plant directive (MCPD) and from landfill boreholes.  

HEMS are not suitable for quantitative measurements to meet the requirements of the Industrial emissions directive (IED). For information on monitoring equipment that meets the monitoring requirements of the IED, see MCERTS for stack emissions monitoring equipment at industrial installations.

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

CSA Group Testing UK Ltd (CSA) 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 – Assessment of air quality monitoring equipment - Part 1: General principles of certification
• EN 15267-2 Air quality – Assessment of air quality monitoring equipment - Part 2: Initial assessment of the manufacturer’s quality management system and post certification surveillance for the manufacturing process

2. Scope

This document specifies the performance characteristics and test procedures for HEMS. The measurands covered include but are not restricted to:

• sulphur dioxide
• oxides of nitrogen
• carbon monoxide and carbon dioxide
• methane
• oxygen
• hydrogen sulphide
• flow rate

3. Testing and certification

The standard you need for the testing of HEMS under MCERTS is ‘EN 15267-4 Air quality – Assessment of air quality monitoring equipment Part 4: Performance criteria and test procedures for portable automated measuring systems for periodic measurements of emissions from stationary sources’.

Regulatory requirements relevant to the testing and certification of HEMS used to monitor medium combustion plants (MCPs) are specified in Monitoring stack emissions: low risk MCPs and specified generators.

HEMS must undergo testing either by a laboratory acceptable to the certification body or you may carry out in-house testing. The certification body must be satisfied that your test facilities meet the requirements for quality assurance. You may also use a combination of both external and in-house testing.

If you decide to carry out in-house testing, you must describe your test facilities to the certification body. You must include provisions for quality assurance and quality control of testing and indicate which tests you want to perform.

When you carry out in-house testing, the results of the tests will be subject to an assessment and supervision by the certification body. The assessment will examine the test methods, test results and traceability.

When applying for certification, you must state the measurands, test ranges and intended process applications. The performance data from testing may indicate that the possible range for each measurand may be greater or less than the nominated range. As lower ranges indicate better performance, you may choose to have a lower range based on the test results.

If you have already performed some tests, you should include any test reports with the application for certification. The certification body will decide if you need to complete any further testing. They will then agree with you where you will complete them, either at your own test facilities or at a third-party test laboratory.

4. Unique identification of HEMS

HEMS must have a unique designation that clearly identifies the equipment as a certified model.

You must reflect any changes in the design that effect the performance of the HEMS in the unique designation of the system. This means you must give the modified HEMS a new model designation or number to distinguish it clearly from previous models.

5. Repairs, maintenance and modifications to certified HEMS

Any spares or replacement parts for certified HEMS must meet the same performance standards as the original parts.

Modifications to certified HEMS are allowed if you can demonstrate that these design changes do not degrade the performance of the handheld system below the MCERTS performance standards.

You must keep detailed records and drawings of all design changes to HEMS. You must also have provisions for design verification, inspection and testing to make sure that the HEMS still meet the required performance standards.

The certification body will conduct assessments of the design changes to HEMS to meet the requirements of product certification. You must notify the certification body of any modifications that may have a significant effect on the performance of the HEMS.

Design modifications or extensions to the range of application of a HEMS may require renewed testing. The extent of this renewed testing will depend on the nature of the modifications.

If there is evidence that a modification has limited effects on the performance of the HEMS, then you may only need to carry out a supplementary test.

In the case of software modifications, you must present documentation to the certification body indicating the nature of the modification and resulting effects on operation and functionality. The certification body will then decide if you need perform any further testing.

6. General requirements

HEMS must have an indicator to show the measured parameter (or parameters) and value.

HEMS must have an output of at least -5% to +105% of the certification range. This is to provide for a living zero reading, which means that the instrument can indicate both positive and negative drift. This requirement does not apply to oxygen monitors which use zirconia sensors.

When you provide the HEMS with a printer, the printer output for each set of data will include a record of the date, time and value of all the specified measurement parameters.

You must equip the HEMS with a security mechanism to prevent unintended and unauthorised adjustment. Security mechanisms can include a key or security code programmed into the handheld system before adjustments are permitted.

Any sampling system will be constructed to prevent damage to the sensor (or sensors) and pump by particulate matter and liquids that may be expected in the application. Verification will be by inspection.

There are no performance characteristics for drop tests or vibration tests. However, if the HEMS has undergone such tests for other purposes, then this will be reported on the certificate.

7. Performance characteristics and test methods – HEMS for stack-emissions monitoring, landfill gas monitors, oxygen and flow

Performance characteristics for HEMS other than those for fugitive emissions monitoring are shown in table 1. The values for individual performance characteristics are expressed as a percentage of the certification range unless otherwise stated.

Table 1: Performance characteristics for HEMS

Performance characteristic	Stack emissions monitors	Landfill gas monitors	Oxygen	Gas flow monitors	Clause in EN 15267-4
Response time	<200s	<60s	<200s	<60s	10.6
Repeatability at zero point	<±5%	<±5%	<±0.4%	N/A	10.7
Repeatability at span point	<±5%	<±5%	<±0.4%	<±5%	10.8
Lack-of-fit	<±5%	<±5%	<±0.4%	<±5%	10.9
Influence of ambient temperature change from 20ºC within specified range at zero point	<±5%	<±10%	<±0.8% (<±1.5% for landfill systems)	<±5%	10.11
Influence of ambient temperature change from 20ºC within specified range at span point	<±5%	<±10%	<±0.8% (<±1.5% for landfill systems)	<±5%	10.11
Cross-sensitivity	<±5%	<±5%	<±0.8%	N/A	10.16
Zero drift (1 hour)	<±3%	<±3%	<±0.3%	N/A	10.10
Span drift (1 hour)	<±3%	<±3%	<±0.3%	N/A	10.10

The performance specifications for oxygen apply to monitoring systems for stack emissions and landfill gas. The performance specifications are expressed as a percentage of volume concentration of oxygen.

The performance specification for the effects of ambient temperature on landfill-gas monitoring-systems is <±1.5%.

8. Test methods for HEMS

Warm up time

You must switch off the HEMS and leave it for a least 24 hours in clean air. After the 24-hour period, switch it on and work out the time taken for it to indicate a stable reading.

Response time

You must carry out this test in accordance with the requirements of EN 15267-4, Clause 10.6.

Repeatability at zero point

You must carry out this test in accordance with the requirements of EN 15267-4, Clause 10.7. You must calculate the repeatability standard deviation at zero point based on at least 5 consecutive individual readings.

Repeatability at span point

The test must be carried out generally in accordance with the requirements of EN 15267-4, Clause 10.8. You must calculate the repeatability standard deviation at span point based on at least 5 consecutive individual readings.

Lack-of-fit

You must carry out this test in accordance with the requirements of EN 15267-4, Clause 10.9.

Influence of ambient temperature

You must carry out this test in accordance with the requirements of EN 15267-4, Clause 10.11. The ambient temperature range is usually +5°C to +40°C. The manufacturer may specify an alternative ambient temperature range. The ambient temperature range will be stated on the certificate.

Cross-sensitivity

You must carry out this test in accordance with the requirements of EN 15267-4, Clause 10.16. You must agree appropriate interferents with the certification body. The sum total of positive deviations and the sum total of negative deviations will be specified.

When determining cross-sensitivity of stack emission monitoring systems, you must use the concentrations of interferents in table 2. You may need to change the concentrations depending on the measuring technique, the type of system involved and the intended application. The interferents must be admitted separately to each other.

Table 2: Recommended minimum concentrations of interferents

Interferent	Concentration	Unit
Oxygen	3 and 21	%
Water vapour	30	%
Carbon monoxide	300	mg/m3
Carbon dioxide	15	%
Methane	50	mg/m3
Nitrous oxide	20	mg/m3
Nitrogen monoxide	300	mg/m3
Nitrogen dioxide	30	mg/m3
Ammonia	20	mg/m3
Sulphur dioxide	200	mg/m3
Sulphur dioxide (if required)	1000	mg/m3
Hydrogen chloride	50	mg/m3
Hydrogen chloride (if required)	200	mg/m3

For landfill gas borehole monitoring systems, you must use a test gas with the composition shown in table 3 to work out cross-sensitivity. The interferents must be admitted together.

Table 3: Interferent concentrations for testing landfill-gas bore-hole monitoring systems

Interferent	Concentration
Carbon dioxide	48%
Methane	48%
Carbon monoxide	70 mg/m3
Hydrogen sulphide	20 mg/m3
Nitrogen	Balance

Zero and span drift

You must carry out this test in accordance with the requirements of EN 15267-4, Clause 10.10.

9. Manufacturer’s quality system

You must have a quality system in place that complies with the requirements of ISO 9001 and the supplementary requirements of EN 15267-2.

You must have an annual assessment managed by the certification body. The purpose of this assessment is to cover the supplementary requirements of EN 15267-2. It is not to repeat the elements which are assessed during routine ISO 9001 certification and surveillance visits.

The assessment will include an evaluation of the provisions for:

• the management and control of the design change process
• manufacturing (process control), final inspection tests and calibration – to ensure reproducibility
• clear identification of MCERTS certified equipment
• assuring that design changes do not degrade instrument performance such that they no longer meet the MCERTS performance standards

You must inform the certification body of any design changes to the HEMS. The certification body will then decide if the current certificate is still valid.

10. What to do next

Find out more about MCERTS product certification on the:

• CSA website
• MCERTS collection on GOV.UK

Contact the Environment Agency if you need any help.

General enquiries

National Customer Contact Centre
PO Box 544
Rotherham
S60 1BY

Email enquiries@environment-agency.gov.uk

Telephone 03708 506 506

Telephone from outside the UK (Monday to Friday, 8am to 6pm GMT) +44 (0) 114 282 5312

Monday to Friday, 8am to 6pm.