9.2.1
General
WARNING. Working at height on stacks when installing, maintaining or calibrating permanent sampling equipment is particularly hazardous. in addition to the physical risks of working at height, there are risks from the weather, exposure to flue gases and exposure to substances used in monitoring tests and analysis and cleaning. Before commencing work it should be ensured that the site risk assessment has been adequately performed and appropriate controls are in place. all personnel should comply with the safety recommendations in Clause 4 and work platforms should conform to the requirements in BS En 13284‑1 and BS En 15259.
NOTE 1 Further information on stack emission monitoring is available from Environment Agency Technical Guidance Note M1 [65], and from Risk assessment guide: Industrial‑emission monitoring, published by the Source Testing Association [66].
information should be made available from the site survey identifying the nature of the process before sampling of the stack gas for the first time; for example, whether it is a steady state or cyclic process, and what the feedstocks and material balances are.
Before installing permanent instruments and systems for regulatory purposes, it should be confirmed that the stack gas has been assessed in accordance with BS iSO 10396, BS iSO 9096 and BS En 15259.
Suitably qualified personnel should have assessed the stack gas.
the choice of periodic manual, periodic instrumented or continuous emissions monitoring (CEMs) should take into account the process, nature of emissions and the requirements in the installation operator’s environmental permit. Periodic monitoring is normally acceptable when sampling a batch process, and whether this should be manual or automatic depends on the variability of the emissions, which dictates the frequency of monitoring as well as the suitability of the specific method employed. Where emissions vary frequently, such that periodic measurement would not be representative, automated CEMs should be used.
Monitoring should be carried out in accordance with BS En 15259, which applies to periodic measurements using standard reference methods, automated measuring systems or CEMs. this standard specifies generic principles and gives minimum requirements for the measurement planning, measurement strategy and reporting of emission measurements of air pollutants, and reference quantities to be carried out in exhaust ducts at plants, it also gives minimum requirements for the design and construction of a plant with
performing emission measurements to air. Periodic monitoring should be carried out in accordance with dd CEn/tS 15675.
NOTE 2 Personnel certified to the Environment Agency’s MCERTS are deemed to be suitably qualified to assess the physical and chemical characteristics of stack gases.
NOTE 3 Guidance on selection of methods for regulatory monitoring is given in Environment Agency Technical Guidance Note M2 [67].
It provides information on each type of monitoring, the techniques and principles employed, relevant standards, including British Standards, and the application, strengths and limitations of each method for each determinand.
NOTE 4 Guidance on the measurement and monitoring of volatile organic compounds to air from industrial installations is given in Environment Agency Technical Guidance Note M16 [68].
NOTE 5 The Environment Agency, where necessary,
produces Method Implementation Documents (MID) to support standard methods. MIDs have been published for BS EN 13284‑1 [69], BS EN 14385 [70] and
BS EN 1948 [71].
9.2.2
Periodic sampling
the position and number of sampling facilities for particulate measurements should be in accordance with BS En 13284‑1, BS iSO 9096 or BS En 15259 as appropriate. Before installing
equipment, it should be confirmed that the gas flow‑stability criteria (velocity and direction) at the sampling points are correct, and the sampling points have been agreed with the equipment manufacturer and installation operator. these standards give recommended
sampling locations. however, if the flow‑stability requirements are not achievable then alternative locations should be identified.
Location requirements for measuring gas concentrations are less exacting than those for monitoring particulates, and depend on the homogeneity of the gases and a positive gas flow. the position and number of sampling facilities for gas concentration measurements in homogenous gas flow should be in accordance with BS iSO 9096, BS iSO 10396 or BS En 15259 as appropriate. Before installation of equipment, the homogeneity of the gas flow should be determined at sampling locations specified in these standards. if the gas is homogenous then only one sample point is needed. if the gas is inhomogeneous a different sample location should be identified or a grid measurement approach used. Where mass emission rates and gas concentrations are required to be monitored, the sampling locations should be the same as for particulates. the sampling locations should be agreed with the equipment manufacturer and installation operator.
9.2.3
Continuous emission monitors (CEMs)
a CEM system is not only the analyser, but also includes:
facilities for taking samples (e.g. probe, sample gas lines,
•
flowmeters and regulator, delivery pump);
facilities for sample conditioning (e.g. dust filter, pre‑separator
•
for disturbing components, cooler, converter);
facilities for recording;
•
any necessary testing and adjusting devices for commissioning
•
and functional checks.
NOTE 6 Stack emission measurements require defined and stable flow conditions at the sample location. This allows the velocity and concentration of the measured component in the stack emission to be determined.
If suitable sampling facilities are not available it will mean that sampling of pollutants cannot be carried out in compliance with the required sampling methods. This means the uncertainty associated with the results is greatly
increased. In these circumstances, meaningful results from stack emissions monitoring cannot be achieved.
NOTE 1 Attention is drawn to Environment Agency MCERTS Method Implementation
Document MID 1 [69], relating to BS EN 13284‑1.
NOTE 2 Guidance for positional requirements for periodic sampling is given in Environment Agency Technical Guidance Note M1 [65].
it should be confirmed that the analyser manufacturer has supplied all the necessary components or identified suitable components and their manufacturers.
CEMs for monitoring both gases and particulates should meet the requirements specified in BS iSO 10155; BS En 13284‑2:2004, QaL1;
BS En 14181 or BS En 15267‑3 as appropriate. CEMs should be assessed for suitability for the determinands to be measured, range for the process where it is being applied, integrity of monitoring data in the specific stack conditions, operating temperature range and documentation to ensure continuing functionality.
Positional requirements for sampling particulates and the minimum number of sampling points are given in BS En 13284‑2.
Sampling positions for CEMs that measure gases should be in accordance with BS iSO 10396 or BS En 15259, and positions for CEMs that measure gas volumetric flow rate should be in accordance with BS iSO 14164.
the location of a non‑intrusive CEM should be within one duct diameter or 1 m, whichever is smaller, upstream of the sample ports for manual sampling and generally vertically in line with one of them.
For intrusive CEM the location should be two duct diameters or 2 m, whichever is smaller, upstream of the manual sampling ports and generally at 45º to one of them.
CEMs should be installed in accordance with the manufacturer’s instructions wherever possible, but where this cannot be done because of sampling point problems, e.g. in old stacks, installation should only take place following consultation with the manufacturer and site operator.
after installation, CEMs systems should be checked for alignment, cleanliness, sampling system integrity, leaks, manual zero and span, linearity, interferences and response time.
NOTE 5 It is a requirement of BS EN 14181 that QAL2 validation and calibration is carried out using standard reference methods and suitably qualified personnel meeting a level of competence specified by the competent authority. BS EN 13284‑2 elaborates on the requirements of BS EN 14181 for particulate‑monitoring CEMs. For installations where BS EN 14181 does not apply, the principles of this standard can still be applied for the quality assurance of CEMs. BS ISO 10155 describes the performance and calibration requirements for particulate‑monitoring CEMs, and is useful for installations where BS EN 13284‑2 does not apply.
NOTE 6 Guidance on the quality assurance of CEMs to BS EN 13284‑2 and BS EN 14181 is given in Environment Agency Technical Guidance Note M20 [76].
NOTE 7 Personnel certified to the Environment Agency’s MCERTS are deemed to be suitably qualified to carry out validation and calibration of CEMs.
Calibration of CEMs systems fitted on installations falling under the Large Combustion Plants (England and Wales) regulations 2002 [74]
or the Waste incineration (England and Wales) regulations 2002 [75]
and related legislation (see table a.1) should be carried out in accordance with BS En 14181.
NOTE 1 The requirements of BS EN 15267‑3 are applied in the UK through the Environment Agency’s MCERTS scheme.
NOTE 2 Attention is drawn to Environment Agency performance standards for gaseous emissions, particulates, temperature, pressure and flow rate [72].
NOTE 3 Attention is drawn to the Environment Agency Method Implementation Document MID 13284‑2 [73].
NOTE 4 Guidance for positional requirements for continuous emission monitoring is given in Environment Agency Technical Guidance Note M1 [65].