Monitoring ambient air: techniques and standards
A summary of the techniques and standards you should use to monitor ambient air.
Applies to England
We have structured this index to help you choose an appropriate monitoring technique and standard.
We list the substances in alphabetical order.
Ammonia and ammonium aerosol
Here are the monitoring techniques and standards.
Monitoring technique 1
Periodic (averaged) sampling.
Measurement of gaseous ammonia concentration by active (pumped) sampling using denuder tubes with subsequent collection of particulate ammonium on back-up filter. Analysis is by ammonium flow injection analysis (AMFIA).
Monitoring standard
There are no CEN, ISO, or BS standards for this technique.
Monitoring technique 2
Periodic (averaged) sampling.
Measurement of gaseous ammonia concentration by diffusive (passive) samplers. Depending on the sampler type, analysis is by either ion chromatography, AMFIA, spectrophotometry or colorimetry.
Monitoring standard
The relevant monitoring standard is EN 17346 Ambient air – Standard method for the determination of the concentration of ammonia using diffusive samplers.
Monitoring technique 3
Periodic (averaged) sampling.
Measurement of gaseous ammonia concentration by diffusive (passive) samplers; analysis by ion chromatography (IC).
Monitoring standard
There are no CEN, ISO, or BS standards for this technique.
Monitoring technique 4
Real time monitoring.
Measurement of gaseous ammonia concentration by continuous direct reading chemiluminescence oxides of nitrogen (NOx) analyser in conjunction with an ammonia converter unit. A twin channel analyser reading NOx, and NOx plus ammonia converted to NOx by the catalyst, allows calculation of ammonia concentration from the difference.
Monitoring standard
There are no CEN, ISO, or BS standards for this technique.
Monitoring technique 5
Real-time monitoring using an open-path approach.
Measurement of gaseous ammonia concentration by FTIR (Fourier transform infrared) -based open-path systems.
Monitoring standard
The relevant monitoring standard is EN 15483 Ambient air quality. Atmospheric measurements near ground with FTIR spectroscopy.
Asbestos
Here are the monitoring techniques and standards.
Monitoring technique 1
Periodic (averaged) sampling.
For monitoring around waste facilities, the method will usually be sampling onto membrane filters at about 8 litres per minute for 1 hour, or 2 litres per minute over a 4-hour period, to achieve a 480l sample volume, followed by fibre-counting by phase contrast microscopy.
Monitoring standard
The relevant monitoring standard is Health and Safety Executive guidance (HSG) 248.
The procedure uses low-flow sampling pumps and membrane filters (mixed esters of cellulose or cellulose nitrate with 0.8-–1.2 µm pore size). The filters are held in electrically conducting cylindrical cowled filter holders. Count the fibres collected on the cleared filter using phase contrast microscopy (PCM) to obtain the countable fibre number concentration in air.
The technique is specific for countable fibres (non-fibrous particles excluded from the count). It is inexpensive, quick and you can use it rapidly on-site. It has continuity with historical epidemiological studies.
The technique is for controlled conditions in premises and workplaces and dusty outdoor conditions with high levels of general environmental dust. This dust can render samples unreadable by PCM.
There can be interference problems because PCM does not positively identify asbestos fibres and may include other fibres in the result. Examples include:
- fibreglass
- anhydrite
- plant fibres
- perlite veins
- gypsum
- some synthetic fibres
- membrane structures
- sponge spicules
- diatoms
- micro-organisms
- wollastonite
Positive identification of asbestos must be by dispersion staining or electron microscopy techniques.
The smallest visible fibres detected are about 0.2 µm in diameter, while the finest asbestos fibres may be as small as 0.02 µm in diameter. This means that for some exposures, substantially more fibres may be present than are counted.
This technique gives a lower detection limit of 0.01 fibres per millilitre of air (10,000 fibres per cubic metre) for a 25 mm diameter filter and a sampled air volume of 480 litres. HSG 248 gives the upper quantification limit as 100 fibres per ml.
You can improve the lower detection limit by increasing the sampled air volume, making it more suitable for measuring ambient environmental levels of asbestos.
For a count of 0 it is 95% probable that the count is less than 3 fibres.
Monitoring technique 2
Periodic (averaged) sampling.
Sampling onto a membrane filter followed by fibre-counting using electron microscopy.
Monitoring standard
The relevant monitoring standards are:
- BS ISO 10312 Ambient air. Determination of asbestos fibres. Direct transfer transmission electron microscopy method
- ISO 13794 Ambient air. Determination of asbestos fibres. Indirect-transfer transmission electron microscopy method
Quantification is by counting of fibres by scanning or transmission electron microscopy (SEM or TEM). But you can positively confirm fibres as asbestos on selected areas of the filter by Selected Area Electron Diffraction (SAED) or Energy Dispersive X-ray Analysis (EDAX). These are facilities available on a TEM. This makes the electron microscope method preferable to the HSG 248 method using PCM, when there are significant levels of non-asbestos fibres in the air.
One practical approach is to divide the exposed filter paper into two halves and immediately analyse the first half by PCM. Then, if necessary, analyse the other half of the filter paper later by SEM or TEM to establish the PCM-equivalent asbestos fibres concentrations.
ISO 10312 describes a standard method for number concentration (fibre counting) of airborne asbestos fibres and structures in a wide range of ambient air situations. This standard uses TEM, which has adequate resolution to allow for the detection of small fibres. When combined with EDAX it allows unequivocal identification of most individual fibres of asbestos.
ISO 13794 also describes a standard method for number concentration (fibre counting) of airborne asbestos fibres. It additionally allows the calculation of total mass concentration of airborne asbestos. The calculation uses lengths, widths, and aspect ratios of the asbestos fibres and bundles, together with the density of the type of asbestos.
A limitation of ISO 10312 is that the number of asbestos fibres incorporated in complex, aggregated structures or particles often exceed the number of isolated fibres and bundles observed. Many fibres may be completely obscured in direct-transfer TEM preparations. Standard method ISO 13794 addresses this using specimen preparation procedures for selective concentration of asbestos fibres and removal of organic, water-soluble, and acid-soluble materials. This disperses most complex clusters and aggregates into their component fibres and bundles. The asbestos in the air sample can now be more accurately quantified by the fibre counting.
You cannot compare results obtained using the ISO 13794 indirect-transfer procedure with those from the ISO 10312 direct-transfer procedure directly. You need a site-specific inter-comparison study that considers the fibre size, asbestos type, and the nature of the source of the airborne asbestos. Electron microscopy can detect much smaller fibres than optical microscopy. Levels of electron microscope-visible fibres per cubic metre are in the range 40-100 fibres/m3 (0.04x10-3 to 0.1x10-3 fibres/ml) for remote areas. And in urban air up to 2400 fibres/m3 (2.4x10-3 fibres/ml). At these low levels, the SEM and TEM provides the best means of analysis.
Benzene
Here are the monitoring techniques and standards.
Monitoring technique 1
Periodic (averaged) sampling.
Sampling by manual, pumped (active) sampling; analysis by thermal or solvent desorption followed by gas chromatography.
Monitoring standard
The relevant monitoring standards are EN 14662-1 or EN 14662-2.
These are European reference methods for benzene. The Directive 2008/50/EC requires that manual measurements for reporting purposes use pumped sampling rather than diffusive sampling.
Measurements made using these standard methods should have an expanded uncertainty at the limit value that does not exceed 25%.
Monitoring technique 2
Periodic (averaged) sampling.
Sampling by diffusive (passive) sampling; analysis by thermal or solvent desorption followed by gas chromatography.
Monitoring standard
The relevant monitoring standards are EN 14662-4 or EN 14662-5.
The standard states a range of component uncertainties that when combined and expanded fulfil the DQO (data quality objective) of 25% for benzene.
Monitoring technique 3
Real-time monitoring (quasi-continuous).
Sampling by automatic pumped (active) sampling with in-situ analysis by gas chromatography.
Monitoring standard
The relevant monitoring standard is EN 14662-3. This is the European reference method.
This standard describes an automated GC method for demonstrating compliance with the Directive limit value for benzene with a one calendar-year reference period. CAMS (continuous ambient monitoring systems) used to report results for this purpose must be product-certified or covered by type approval. CAMS certified under MCERTS meet the performance criteria in the CEN standards and the relevant Directive DQO.
Measurements made using this standard method should have an expanded uncertainty at the limit value that does not exceed 25%.
Monitoring technique 4
Real-time monitoring (open path approach).
Differential optical absorption spectroscopy (DOAS) based open-path systems.
Monitoring standard
The relevant monitoring standard is EN 16253: Air quality. Atmospheric measurements near ground with active DOAS. Ambient air and diffuse emission measurements. It is the European reference method.
Measurements made using this standard method should have an expanded uncertainty at the limit value that does not exceed 25%.
Monitoring technique 5
Real-time monitoring (open path approach).
FTIR based open-path systems.
Monitoring standard
The relevant monitoring standard is EN 15483: Ambient air quality. Atmospheric measurements near ground with FTIR spectroscopy.
Measurements made using this standard method should have an expanded uncertainty at the limit value that does not exceed 25%.
Bioaerosols
See Environment Agency TGN M9 Environmental of bioaerosols at regulated facilities.
Carbon disulfide
Here are the monitoring techniques and standards.
Monitoring technique 1
Periodic (averaged) sampling.
Pumped (active) sampling onto solid sorbent tubes; analysis by GC-FPD (flame photometric detector), GC-PID (photo ionisation detector) or GC-TCD (thermal conductivity detector).
Monitoring standard
The relevant monitoring standard is based on the either of the following workplace methods: MDHS 15 or NIOSH 1600.
Sampling is on to charcoal adsorption tubes at 500 ml/min, but this may need modification for ambient levels (for example, increase volume sampled). This is followed by solvent (toluene) desorption; analysis by GC, with FPD (although you can also use a PID or thermal conductivity detector).
Monitoring technique 2
Real time monitoring.
Measurement by continuous sampling with batch analysis by chromatographic sulfur gas analyser (GC-FPD or GC-PID).
Monitoring standard
There is no CEN, ISO, or BS standard method for this technique.
Carbon monoxide
Here are the monitoring techniques and standards.
Monitoring technique 1
Real-time monitoring.
Measurement by continuous direct-reading non-dispersive infrared (NDIR) analyser.
Monitoring standard
The relevant monitoring standard is EN 14626 Ambient air. Standard method for the measurement of the concentration of carbon monoxide by non-dispersive infrared spectroscopy.
This is the European reference monitoring method for demonstrating compliance with the Directive limit value. CAMS used to report results for this purpose must be product-certified or covered by type approval. CAMS certified under MCERTS meet the performance criteria in the CEN standards and the relevant Directive DQO.
Measurements made using this method should have an expanded uncertainty at the limit value that does not exceed 15%.
Monitoring technique 2
Real-time monitoring.
Low-cost sensors with a measurement principle using either electrochemical cells, metal-oxide semiconductor sensors, or light absorption.
Monitoring standard
The relevant monitoring standard is CEN/TS 17660-1 Air quality - Performance evaluation of air quality sensor systems - Part 1: Gaseous pollutants in ambient air.
This technical specification is consistent with the requirements for indicative measurements and objective estimation defined in Directive 2008/50/EC. It also provides a classification for non-regulatory measurements that require more relaxed performance criteria.
You cannot use low-cost sensors as direct replacements for reference monitors.
Monitoring technique 3
Real-time monitoring (open-path approach).
FTIR-based open-path systems.
Monitoring standard
The relevant monitoring standard is EN 15483: Ambient air quality. Atmospheric measurements near ground with FTIR spectroscopy.
Measurements made using this method should have an expanded uncertainty at the limit value that does not 15%.
Dioxins and furans
Here are the monitoring techniques and standards.
Monitoring technique
Periodic (average) sampling.
Pumped (active) sampling onto filters and traps; analysis by gas chromatography with mass spectrometry (GC-MS).
Monitoring standard
The relevant monitoring standard for the analysis is EN 1948-3: Stationary source emissions. Determination of the mass concentration of PCDDs or PCDFs and dioxin-like PCBs. Identification and quantification of PCDDs or PCDFs.
Dioxin-like polychlorinated biphenyls
Here are the monitoring techniques and standards.
Monitoring technique
Periodic (average) sampling.
Pumped (active) sampling onto filters and traps; analysis by GC-MS.
Monitoring standard
The relevant monitoring standard for analysis is EN 1948-4 Stationary source emissions. Determination of the mass concentration of PCDDs or PCDFs and dioxin-like PCBs. Identification and quantification of PCDDs or PCDFs.
Elemental and organic carbon in particulate matter
Here are the monitoring techniques and standards.
Monitoring technique
Periodic (average) sampling.
Pumped active sampling onto filters. The sampling process determines:
- the size fraction of the particulate matter
- the retention of semi-volatile material
- the uptake or loss of volatile organic compounds on the filter at the time of sampling.
Monitoring standard
The relevant monitoring standard is EN 16909: Ambient air - Measurement of elemental carbon (EC) and organic carbon (OC) collected on filters.
Formaldehyde and other aldehydes
Here are the monitoring techniques and standards.
Monitoring technique 1
Periodic (average) sampling.
Pumped (active) sampling onto coated sorbent cartridges; analysis of formaldehyde and other carbonyl compounds (aldehydes and ketones) by HPLC (high performance liquid chromatography).
Monitoring standard
The relevant monitoring standard for analysis is ISO 16000-3: Indoor air. Determination of formaldehyde and other carbonyl compounds in indoor air and test chamber air. Active sampling method.
The sampling procedure is based on US Environmental Protection Agency (EPA) method TO-11A. It gives a time-weighted average (TWA) sample and can be used for long-term (1 h to 24 h) or short-term (5 min to 60 min) sampling. The method is specific to formaldehyde but, with modification, you can detect and quantify at least 12 other carbonyl compounds:
- acetaldehyde
- acetone
- benzaldehyde
- butyraldehyde
- valeraldehyde
- 2,5-dimethylbenzaldehyde
- capronaldehyde
- isovaleraldehyde
- propionaldehyde
- o-tolualdehyde
- m-tolualdehyde
- p-tolualdehyde
It is not suitable for longer chained carbonyl compounds.
Monitoring technique 2
Sampling of formaldehyde by diffusive (passive) sampling onto sorbent tube; analysis by HPLC.
Monitoring standard
The relevant monitoring standard for analysis is ISO 16000-4: Indoor air. Determination of formaldehyde. Diffusive sampling method.
Monitoring technique 3
Real-time monitoring (open path approach).
Differential optical absorption spectroscopy (DOAS) based open-path systems.
Monitoring standard
The relevant monitoring standard is EN 16253: Air quality. Atmospheric measurements near ground with active DOAS. Ambient air and diffuse emission measurements.
Measurements made using this method should have an expanded uncertainty at the limit value that does not exceed 15 to 25%.
Monitoring technique 4
Real-time monitoring (open path approach).
FTIR based open-path systems.
Monitoring standard
The relevant monitoring standard is EN 15483.
Measurements made using this method should have an expanded uncertainty at the limit value that does not exceed 15 to 25%.
Halogenated volatile organic compounds
Here are the monitoring techniques and standards.
Monitoring technique 1
Periodic (average) sampling.
Sampling of volatile organic compounds (VOCs) by pumped (active) sampling onto sorbent tube, and analysis by thermal desorption or capillary gas chromatography.
Monitoring standard
The relevant monitoring standard is EN ISO 16017-1: Indoor, ambient and workplace air. Sampling and analysis of volatile organic compounds by sorbent tube or thermal desorption or capillary gas chromatography. Pumped sampling.
Monitoring technique 2
Real-time monitoring (intermittent, non-continuous).
Measurement of halogenated hydrocarbons by portable gas chromatography.
Monitoring standard
There is no CEN, ISO, or BS standard method for this technique.
Monitoring technique 3
Real-time monitoring.
Measurement of halogenated hydrocarbons by continuous sampling with batch analysis by automated in-situ gas chromatography.
Monitoring standard
You can apply the same approach as EN 14662-3 (benzene).
You can measure halogenated hydrocarbons by automatically cycling GC systems, using a suitable pre-concentration technique such as cryogenic trapping to provide a concentrated sample for analysis. These systems are suitable for unattended operation in air quality monitoring networks.
Heavy metals (excluding mercury)
Here are the monitoring techniques and standards.
Monitoring technique 1
Periodic (average) sampling.
Measurement of airborne concentrations of particulate metals (lead, cadmium, arsenic, and nickel) is by pumped (active) sampling onto filters. Analysis is by graphite furnace atomic absorption spectrophotometry (GF-AAS) or inductively coupled plasma with mass spectrometry (ICP-MS).
Monitoring standard
The relevant monitoring standard is EN 14902 Ambient air quality. Standard method for the measurement of lead, cadmium, arsenic, and nickel in the PM10 fraction of suspended particulate matter.
This is the European reference monitoring method for demonstrating compliance with the Air Quality Directive (2008/50/EC) limit value for lead in the PM10 fraction of suspended particulate matter. It is also the European reference monitoring method for demonstrating compliance with the 4th Daughter Directive Target Values for arsenic, cadmium, nickel in the PM10 particulate fraction of ambient air.
Measurements made using this standard method should have an expanded uncertainty at the limit value that does not exceed 25% for lead and 40% each for arsenic, cadmium and lead.
Monitoring technique 2
Periodic (average) sampling.
Measurement of deposition rates of metals (lead, cadmium, arsenic, and nickel) by non-automatic, passive (deposition) sampling into a deposition gauge. Analysis by GF-AAS or ICP-MS.
Monitoring standard
The relevant monitoring standard is EN 15841: Ambient air quality. Standard method for determination of arsenic, cadmium, lead, and nickel in atmospheric deposition.
This is the European reference monitoring method for measuring the deposition rates of arsenic, cadmium, nickel for the EU 4th Daughter Directive. Defra use it in its UK Heavy Metals Network.
The method is applicable for deposition measurements in rural areas, industrial areas, or urban areas.
Measurements made using this standard method should have an expanded uncertainty at the limit value that does not exceed 70% for deposition.
Monitoring technique 3
Periodic (average) sampling.
Measurement of airborne concentration of particulate lead by pumped (active) sampling onto filters. Analysis by AAS.
Monitoring standard
The relevant monitoring standard is ISO 9855: Methods for measurement of air pollution. Determination of the particulate lead content of aerosols collected on filters: atomic absorption spectrometric method.
Hydrogen sulfide and inorganic reduced sulfur compounds
Here are the monitoring techniques and standards.
Monitoring technique 1
Periodic (average) sampling.
Sampling of hydrogen sulfide by diffusive (passive) samplers; analysis by UV-visible spectrophotometry.
Monitoring standard
There is no CEN, ISO, or BS standard method for this technique.
Monitoring technique 2
Periodic (average) sampling.
Pumped (active) sampling of hydrogen sulfide through an impinger bottle with absorption in cadmium hydroxide suspension, analysis by visible spectrophotometry.
Monitoring standard
The relevant monitoring standard is ISC method 42402-01-70T Methylene Blue Method. Lodge JP (ed), Methods of Air Sampling and Analysis, 3rd Edn., Intersociety Committee, Lewis Publ Inc, 1989.
Air is bubbled through an alkaline suspension of cadmium hydroxide (10 ml) in a midget impinger (25 ml capacity) with coarse-porosity frit. This precipitates the sulfide as cadmium sulfide (the sulfide suffers rapid air oxidation in aqueous alkaline solution), and addition of Arabinogalactan minimises photodecomposition. Determine the collected sulfide by spectrophotometric measurement of the methylene blue produced by the reaction with a strongly acid solution of N,N-dimethyl-p-phenylenediamine and ferric chloride.
Avoid extended sampling (for example, 24-h integrated samples) as losses can result and complete analysis within 24 h. The methylene blue reaction is highly specific for sulfide at ambient concentrations. Some interferences occur from nitrite (>0.3 ppm) and ozone (15% at 57 ppb).
Monitoring technique 3
Real time monitoring.
Measurement of hydrogen sulfide by continuous UV-fluorescence analyser.
There is currently no CEN, ISO, or BS standard method for this technique.
Monitoring technique 4
Real time monitoring.
Measurement of total sulfides by continuous flame-photometric analyser.
Monitoring standard
There is no CEN, ISO, or BS standard method for this technique.
Monitoring technique 5
Real time monitoring.
Measurement of hydrogen sulfide by continuous sampling with batch analysis by gas chromatography (GC).
Monitoring standard
There is no CEN, ISO, or BS standard method for this technique.
Monitoring technique 6
Real-time monitoring.
Low-cost sensors with a measurement principle using either electrochemical cells, metal-oxide semiconductor sensors, or light absorption.
Monitoring standard
CEN/TS 17660-1: Air quality - Performance evaluation of air quality sensor systems - Part 1: Gaseous pollutants in ambient air.
Monitoring technique 7
Measurement of total sulfides by continuous flow colorimetric analyser.
Monitoring standard
There is no CEN, ISO, BS, or MCERTS standard for this technique.
Inorganic acids (HNO3, HCl, HF, HBr, H3PO3)
Here is the monitoring technique and standard.
Monitoring technique
Active sampling of gaseous HNO3, HCl and HF by denuder tubes; analysis by ion chromatography.
Monitoring standard
There is no CEN, ISO, or BS standard method covering this technique.
Man-made mineral fibres
Here are the monitoring techniques and standards.
Monitoring technique 1
Real time monitoring.
Active (pumped) sampling onto a cellulose ester membrane filter. Quantification by gravimetric determination, or fibre counting by polarised light microscopy.
Monitoring standard
Health and Safety Executive guidance MDHS 59/2 Machine-made fibres - Airborne number concentration and classification by phase contrast light microscopy.
You can modify this method by increasing the sampled volume to provide an improved lower detection limit. The gravimetric approach is not well suited to the ambient atmosphere because the method is non-specific and other atmospheric dusts would interfere significantly. Fibre counting is not suited to very dusty atmospheres. If you experience difficulties with interferences with PCM, then you should use TEM or EDAX (or both) as the end method.
Mercaptans
Here are the monitoring techniques and standards.
Monitoring technique 2
Periodic (average) sampling.
Pumped (active) sampling of mercaptans through an impinger bottle with absorption in cadmium hydroxide suspension, analysis by spectrophotometry.
Monitoring standard
ISC method 43901-01070T for mercaptans. Lodge JP (ed), Methods of Air Sampling and Analysis, 3rd Edn., Intersociety Committee, Lewis Publ Inc, 1989.
Mercury
Here are the monitoring techniques and standards.
Monitoring technique 1
Periodic (average) sampling.
Measurement of airborne concentration of total gaseous mercury - pumped (active) sampling onto sorbent tubes, analysis by mercury analyser with fluorescence detector.
Monitoring standard
The relevant monitoring standard is EN 15852:2010 Ambient air quality - Standard method for the determination of total gaseous mercury.
This is the European reference monitoring method for monitoring of total gaseous mercury.
Measurements made under the Directive must have an expanded uncertainty at the Limit Value that does not exceed the DQO of 50% for total gaseous mercury.
Monitoring technique 2
Periodic (average) sampling.
Measurement of deposition rates of mercury by non-automatic, passive (deposition) sampling into a deposition gauge. Analysis by cold vapour atomic absorption spectrometry or cold vapour atomic fluorescence spectrometry.
Monitoring standard
The relevant monitoring standard is EN 15853 Ambient air quality. Standard method for determination of mercury deposition.
This is the European reference monitoring method for measuring the deposition rate of mercury.
Monitoring technique 3
Periodic (average) sampling.
Measurement of airborne concentrations of speciated mercury - pumped (active) sampling onto denuder tube and trap; analysis by cold-vapour atomic fluorescence spectrophotometry (CV-AFS).
Monitoring standard
There is no CEN, ISO, or BS standard method for this technique.
Nitrogen oxides
Here are the monitoring techniques and standards.
Monitoring technique 1
Periodic (average) sampling.
Diffusion tube (passive) sampling; followed by extraction and analysis by colorimetry or ion chromatography (IC).
Monitoring standard
The relevant monitoring standard is EN 16339: Ambient air - Method for the determination of the concentration of nitrogen dioxide by diffusive sampling.
No full demonstration of equivalence to the European reference method has been performed. However, the standard notes that some annual-average comparison studies with chemiluminescence showed the potential for diffusive sampling to meet the DQO of 15% expanded uncertainty for fixed measurements.
For typical sample-collection periods of 1 to 4 weeks the nitrogen dioxide measurement concentration range is approximately 3 µg/m3 to 130 µg/m3.
The relative expanded uncertainty using these tube-type diffusive samplers can potentially be better than 25% for individual measurements. When aggregating results to give annual average values, this may be reduced to better than 15 % because of the reduction of random effects on uncertainty.
Monitoring technique 2
Periodic (average) sampling.
Diffusion tube (passive) sampling; analysis by Griess-Saltzman method.
Monitoring standard
You should comply with Diffusion Tubes for Ambient NO2 Monitoring: Practical Guidance.
Palmes-type diffusion tubes are widely used in the UK for indicative measurements of ambient nitrogen dioxide for the purposes of LAQM.
The lower detection limit is better than 0.5 ppb for 2-week exposures.
The quoted measurement uncertainty is ±25%.
Monitoring technique 3
Real-time monitoring.
Measurement by continuous direct reading chemiluminescence analyser.
Monitoring standard
The relevant monitoring standard is EN 14211: Ambient air quality. Standard method for the measurement of the concentration of nitrogen dioxide and nitrogen monoxide by chemiluminescence.
This is the European reference monitoring method for demonstrating compliance with the Directive limit values. CAMS used to report results for this purpose must be product-certified or covered by type approval. CAMS certified under MCERTS meet the performance criteria in the CEN standards and the relevant directive DQO.
Measurements made using this standard method should have an expanded uncertainty at the limit value that does not exceed 15% for nitrogen dioxide or NOx.
Monitoring technique 4
Real-time monitoring.
Low-cost sensors with a measurement principle using either electrochemical cells, metal-oxide semiconductor sensors, or light absorption.
Monitoring standard
CEN/TS 17660-1: Air quality - Performance evaluation of air quality sensor systems - Part 1: Gaseous pollutants in ambient air.
Monitoring technique 5
Real-time monitoring (open path approach).
DOAS based open-path systems.
Monitoring standard
The relevant monitoring standard is EN 16253: Air quality. Atmospheric measurements near ground with active differential optical absorption spectroscopy (DOAS). Ambient air and diffuse emission measurements.
Measurements made using this standard method should have an expanded uncertainty at the limit value that does not exceed 15% for nitrogen dioxide or NOx.
Monitoring technique 6
Real-time monitoring (open path approach).
FTIR based open-path systems.
Monitoring standard
The relevant monitoring standard is EN 15483: Ambient air quality. Atmospheric measurements near ground with FTIR spectroscopy.
Measurements made using this standard method should have an expanded uncertainty at the limit value that does not exceed 15%.
Nuisance dust (dustfall)
Dustfall is nuisance dust falling out of the air in a nominally vertical direction and depositing onto a horizontal surface.
Here are the monitoring techniques and standards.
Monitoring technique 1
Periodic (average) sampling.
Measurement of deposition rate (mg/m2/day): sampling by passive collection of dust into a Frisbee deposit gauge; gravimetric analysis.
Monitoring standard
Stockholm Environment Institute at York (SEI-Y) method (Vallack, H.W. (1995), A Field Evaluation of Frisbee-Type Dust Deposit Gauges, Atmospheric Environment, 29. 1465-1469).
You can use a polyester foam dust trap to reduce contamination from falling leaves. The inverted Frisbee is mounted horizontally on a pole 1.75 m above the ground. Deposited matter on the collection surface, and the insoluble matter in the rainwater collection bottle are quantitatively removed and separated by gentle vacuum filtration. Insoluble matter is dried and determined gravimetrically. Express deposition rate as mg/m2/day.
The Frisbee has superior collecting efficiency and aerodynamic characteristics that make it suitable for short-term sampling periods of about a week. But it is usually exposed for longer as custom and practice default nuisance limits are based on monthly exposures.
You can measure deposition rate from a particular direction using a directional Frisbee gauge. Here the collection surface is exposed only when the associated meteorological equipment indicates that wind is from a defined direction arc. However, the need for meteorological equipment and power limits application for routine monitoring.
Gravimetric determination on a 0.1 mg resolution balance with a one-month sampling period gives a theoretical LOD (limit of detection) of 0.07 mg/m2/day.
Monitoring technique 2
Periodic (average) sampling.
Measurement of soiling rate, as soiling units (SU) per week: sampling by passive collection of dust onto a horizontally positioned microscope slide; analysis by measuring the change in specular reflectance.
Monitoring standard
Schwar MJR, A Dust Meter for Measuring Dust Deposition and Soiling of Glossy Surfaces, Clean air, Vol. 24, No.4, pp 164-169, 1994.
Developed for assessing the annoyance effect of deposited dust on glossy surfaces, for example, windowsills and cars. Expose a clean microscope slide for, typically, one week. Position the slide horizontally on a surface between 1 m and 2 m above the ground. Quantify the dustiness of the exposed slide by measuring the reduction in specular reflectance relative to a clean unexposed slide using a reflectomer instrument. Obtain a measurement in SU by subtracting the reflectance value from 100. You can relate the soiling level to perceived annoyance. You can conduct cost effective large or detailed surveys using microscope slide samplers.
Monitoring technique 3
Periodic (average) sampling.
Measurement of soiling rate, as percentage effective area coverage (EAC) per week. Sampling is by passive collection of dust onto a horizontally positioned white sticky Fablon pad and analysis by measuring the change in reflectance.
Monitoring standard
Bearman and Kingsbury, Assessment of Nuisance from Deposited Particulates Using a Simple and Inexpensive Measuring System, Clean Air, Vol.11, No.2, pp77-81, 1981.
Developed for assessing the annoyance from soiling of surfaces, for example, windowsills and cars. Similar application to the dust slide method. Inexpensive Fablon samplers allow you to carry out large or detailed surveys at modest cost. Standard sampling exposure period is 7 days. The soiling of the exposed sticky pad is measured using a reflectance meter and expressed as the percentage EAC per day, which you can be relate to complaint levels.
Nuisance dust (flux)
Dust flux is nuisance dust that moves in a direction approximately parallel to the ground or depositing out of the air onto a nominally vertical surface (for example, a wall of a building).
Here are the monitoring techniques and standards.
Monitoring technique 1
Periodic (average) sampling.
Measurement of dust flux rate (mg/m2/day). Sampling is by passive collection of dust into a directional dust gauge. Analysis by optical (obscuration) end-method (although popular variation from standard is gravimetric analysis).
Monitoring standard
The relevant monitoring standard is BS 1747-5: Directional dust gauges.
Dust flux gauges have a collection device positioned in the vertical plane to intercept dust as it travels parallel to the ground. This approach is best suited for monitoring dust releases across the site boundary.
The BS (also known as CERL-type) directional dust gauge has four slotted sampling tubes with collection pots set at right angles to each other, with either the sampling slot of each tube lined up with the four ordinate points of the compass, or one slot towards the pollution source. Place an aqueous suspension of the dust collected in each pot in a water-filled glass cell. Estimate the dust loading by the amount of obscuration of a beam of light passing through the cell. You can only use this end method where a very large percentage of the total dust is from one source and the dust has approximate reproducible composition and density. Although you express the results in units of mg/m2/day (for each direction), this is the mass flux rate, not the deposition rate. So, the results are not comparable with those of a deposition gauge.
Sampling periods of about 10 days to 1 month are usual and long sampling programmes of about one year are necessary.
Gravimetric determination on a 0.1 mg resolution balance with a one-month sampling period gives a theoretical LOD of 6.5 mg/m2/day for each of the four directions.
Monitoring technique 2
Periodic (average) sampling.
Measurement of soiling rate, as percentage effective area coverage (%EAC) per week.
Sampling by passive collection of dust onto a vertically positioned white sticky Fablon sheet (which you can wrap around a cylinder to form a directional gauge).
Analysis by measuring the change in reflectance.
Monitoring standard
Standard sampling exposure period is 7 days. The soiling of the exposed sticky pad is measured using a reflectance meter and expressed as the percentage %EAC per day, which can be related to complaint levels.
A commercially available sampling and analysis system allows the summarising of the direction of dust flux (as pollution roses) in, typically, 15° arcs about the monitoring point. Further information is provided in Low Cost Directional Monitoring of Nuisance Dust Around Mineral Workings, funded by the Mineral Industry Sustainable Technology (MIST) programme.
Odour
See the H4 guidance on odour management.
Ozone
Here are the monitoring techniques and standards.
Monitoring technique 1
Periodic (average) sampling.
Sampling by diffusive (passive) samplers; analysis by IC.
Monitoring standard
A passive sampler (the 8-h ozone radial diffusive sampler) has been fully validated (according to the CEN protocol for the validation of diffusive samplers) for monitoring 8-h ozone concentrations in ambient air. All the parameters regarding the sampler characteristics were consistent with the requirements of this protocol apart from the blank value. You must evaluate and subtract this at each sampling. Using an empirical model to allow for temperature and humidity effects on the uptake rate, the method meets the DQO of 15% for ozone. Therefore, the sampler represents an appropriate indicative method.
Standard sampling period for a single exposure is 2 weeks, at which the lower detection limit is 2 ppb.
Monitoring technique 2
Real-time measurement.
Monitoring standard
The relevant monitoring standard is EN 14625: Ambient air quality. Standard method for the measurement of the concentration of ozone by ultraviolet photometry.
This is the European reference monitoring method for demonstrating compliance with the EU Directive Limit Values. CAMS used to report results for this purpose must be product-certified or covered by type approval. CAMS certified under MCERTS meet the performance criteria in the CEN standards and the relevant Directive data quality objective.
The type-approval test for this standard to requires instruments to have:
- concentration range covering is 0-500 µg/m3
- a repeatability at zero of £1.0 ppb
- a response time of £180 sec
Measurements made using this standard method should have an expanded uncertainty at the limit value that does not exceed 15%.
Monitoring technique 3
Real-time monitoring.
Low-cost sensors with a measurement principle using either electrochemical cells, metal-oxide semiconductor sensors, or light absorption.
Monitoring standard
The relevant monitoring standard is CEN/TS 17660-1: Air quality - Performance evaluation of air quality sensor systems - Part 1: Gaseous pollutants in ambient air.
Particle number concentration
Here are the techniques and standards.
Monitoring technique 1
Real-time monitoring.
Condensation particle counter (CPC) operated in counting mode.
Monitoring standard
The relevant monitoring standard is CEN/TS 16976: Ambient air. Determination of the particle number concentration of atmospheric aerosol.
Particle number size distribution
Real-time monitoring.
Here are the techniques and standards.
Monitoring technique 1
Mobility particle size spectrometer used with a bipolar diffusion charger and a CPC detector.
Polycyclic aromatic hydrocarbons (PAHs)
Here are the monitoring techniques and standards.
Monitoring technique 1
Periodic (average) sampling.
Non-automatic, pumped (active) sampling of PAHs onto filters and traps over 24-hour duration. Analysis by gas chromatography with mass spectrometry.
Monitoring standard
The relevant monitoring standard is EN 15549: Air quality. Standard method for the measurement of the concentration of benzo(a)pyrene in ambient air.
This is the European reference monitoring method for airborne concentrations of PAHs.
Measurements made using this standard method should have an expanded uncertainty at the limit value that does not exceed 50% for benzo(a)pyrene.
Monitoring technique 2
Periodic (average) sampling.
Non-automatic, passive (deposition) sampling of PAHs into standardised funnel-bottle bulk collector. Analysis by GC-MS, or HPLC with fluorescence detection.
Monitoring standard
The relevant monitoring standard is EN 15980: Air quality. Determination of the deposition of benz[a]anthracene, benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenz[a,h]anthracene and indeno[1,2,3-cd]pyrene.
This is the European reference monitoring method for measuring PAH deposition rates for demonstrating compliance with the EU 4th Daughter Directive Target Value set for the PAH ’marker’, benzo(a)pyrene.
Measurements made to the European reference method using compliant and equivalent instruments will have an expanded uncertainty at the limit value that does not exceed the DQO of 70% for deposition.
Monitoring technique 3
Periodic (average) sampling.
Non-automatic pumped (active) sampling of PAHs as part of PM10. Analysis by HPLC with fluorescence detection or by GC-MS.
Monitoring standard
The relevant monitoring standard is CEN/TS 16645: Ambient air - Method for the measurement of benz[a]anthracene, benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene, dibenz[a,h]anthracene, indeno[1,2,3-cd]pyrene and benzo[ghi]perylene.
This technical specification refers to the measurement of PAHs not covered in EN 15449. The PAHs are measured in ambient air, whereas EN 15449 refers to a deposition measurement.
Sulfur dioxide
Here are the monitoring techniques and standards.
Monitoring technique 1
Periodic (average) sampling.
Sampling by diffusive (passive) samplers; analysis by ion chromatography (IC).
Monitoring standard
There is no CEN, ISO of BS standard method for this technique.
EN 13528 specifies generic performance requirements for ambient air diffusive samplers.
Consists of a diffusion tube with potassium hydroxide absorbent. The ingress of sulfur-containing particles (for example diesel fumes) is prevented by a 1 µ filter. Exposed samples are extracted into deionised water and analysed for sulfate by ion chromatography.
Recommended exposure period between 1 and 4 weeks, so it is not suitable for short-term episodes. The usual applications, benefits and limitations of diffusive sampling apply.
Monitoring technique 2
Real-time measurement.
Measurement by continuous direct-reading UV fluorescence analyser.
Monitoring standard
The relevant monitoring standard is EN 14212: Ambient air. Standard method for the measurement of the concentration of sulfur dioxide by ultraviolet fluorescence.
This is the European reference monitoring method for demonstrating compliance with the Directive limit values. CAMS used to report results for this purpose must be product-certified or covered by type approval. CAMS certified under MCERTS meet the performance criteria in the CEN standards and the relevant directive DQO.
Measurements made using this standard method should have an expanded uncertainty at the limit value that does not exceed 15%.
Monitoring technique 3
Real-time monitoring.
Low-cost sensors with a measurement principle using either electrochemical cells, metal-oxide semiconductor sensors, or light absorption.
Monitoring standard
CEN/TS 17660-1: Air quality - Performance evaluation of air quality sensor systems - Part 1: Gaseous pollutants in ambient air.
Monitoring technique 4
Real-time monitoring – open-path approach.
DOAS-based open-path systems.
Monitoring standard
The relevant monitoring standard is EN 16253: Air quality. Atmospheric measurements near ground with active differential optical absorption spectroscopy (DOAS). Ambient air and diffuse emission measurements.
Measurements made using this standard method should have an expanded uncertainty at the limit value that does not exceed 15%.
Sulfur (total)
Here are the monitoring techniques and standards.
Monitoring technique 1
Real time monitoring.
Measurement of total sulfur molecules by continuous flame-photometric analyser.
Monitoring standard
There is no CEN, ISO, or BS standard method for this technique.
Monitoring technique 2
Real time monitoring.
Measurement of total reduced organic sulfur species by continuous PID.
Monitoring standard
There is no CEN, ISO, or BS standard method for this technique.
Suspended particles as black smoke or black carbon
Here are the monitoring techniques and standards.
Monitoring technique 1
Periodic (average) sampling.
Pumped sampling of black smoke onto filter paper; optical analysis (reflectance).
Monitoring standard
The relevant monitoring standard is ISO 9835: Ambient air – Determination of a black smoke index.
You collect daily average samples on Whatman No.1 cellulose filter papers. You use a reflectometer to measure the darkness of stain produced by collected particulates. Convert the reflectance value to International Equivalent Standard Smoke (µg/m3) using a calibration curve.
The sample inlet, an upturned funnel, is not specifically designed to be size selective, although one study has shown that it collects the approximate size fraction PM4.5 (Air Pollution in the UK: 2007, AEA report for Defra and the Devolved Administrations).
The maximum measurable reflectance is between 99% and 99.9%, giving a lower detection limit of between 0.1 and 0.9 µg/m3.
At the low average concentrations at many sites the provisional uncertainty is around 30%, dominated by the repeatability of the reflectance measurement on real filter samples. At higher black smoke concentrations, the provisional uncertainty is estimated to be around 14% (2007 Annual Report for the UK Black Smoke Network).
Monitoring technique 2
Real-time monitoring.
Aethalometers, measuring black carbon using a real-time optical transmission technique.
Monitoring standard
The relevant monitoring standard is EN/TR 16243.
The LOD is proportional to flow rate (hence inversely proportional to time-resolution) and is- approximately 0.1 µg/m3 at 1-minute resolution at 3 l/min-
The 2013 annual report for the UK Black Carbon Network (available on Defra’s UK Air webpages) indicates overall measurement uncertainty is 11% for annual averaging period and 15% for an hourly average.
Suspended particulate matter as PM10 or PM2.5
Here are the monitoring techniques and standards.
Monitoring technique 1
Periodic (average) sampling.
Pumped (active) sampling of PM10 and PM2.5 onto filter paper; Gravimetric analysis.
Monitoring standard
The relevant monitoring standard is EN 12341: Ambient air. Standard gravimetric measurement method for the determination of the PM10 or PM2.5 mass concentration of suspended particulate matter.
This is the European reference monitoring method for demonstrating compliance with Directive limit values. It is a manual, gravimetric method, in which you determine the mass of particles collected by weighing after sampling a known volume of air.
Measurements are performed with samplers with inlet designs as specified in Annex A of EN 12341. They operate at a nominal flow rate of 2.3 m3/h, over a nominal sampling period of 24 h. This Standard covers the use of sequential samplers (equipped with an automatic filter changer allowing extended stand-alone operation) and the use of single-filter samplers.
This European Standard does not give procedures for the demonstration of equivalence of other sampler types, (for example, equipped with a different aerosol classifier or operating at different flow rates). You can find details of such procedures and requirements in the Defra guide Demonstration of Equivalence of PM Monitoring Methods.
Equipment for use as reference samplers should comply fully with EN 12341. However, older versions of these 2.3 m3/h samplers have a special status as reference samplers and historical results obtained using these samplers will remain valid. They do not employ sheath air cooling, the ability to cool filters after sampling, or to monitor temperatures at critical points in the sampling system. You can still use these samplers for monitoring purposes and for equivalence trials, if you make a well justified additional allowance to their uncertainties. In addition, the following specific sampling systems also retain a special status for use as reference samplers:
- the long nozzle, 2.3 m3/h sampler
- the 68 m3/h sampler for PM10 in EN 12341
- the 30 m3/h PM2.5 inlet in EN 14907
Certain other sampling systems listed in the standard, can be used if you make a well justified additional allowance to their uncertainties as derived from equivalence tests.
Measurements made using this standard method should have an expanded uncertainty at the limit value that does not exceed 25% for PM10 or PM2.5.
Monitoring technique 2
Real-time monitoring.
Automated CAMS, such as those based on the use of oscillating microbalances, ß-ray attenuation, or in-situ optical methods.
Monitoring standard
The relevant monitoring standard is EN 16450 Ambient air. Automated measuring systems for the measurement of the concentration of particulate matter (PM10; PM2.5).
This is the European reference monitoring method for demonstrating compliance with the Directive limit values using CAMS.
Measurements made using this standard method should have an expanded uncertainty at the limit value that does not exceed 25% for PM10 or PM2.5.
Monitoring technique 3
Real-time monitoring.
Light-scattering optical particle counter.
Monitoring standard
There is no CEN, ISO of BS standard method for this technique.
You can use these for screening surveys and for ongoing indicative monitoring surveys. They are not suitable for demonstrating compliance with limit values.
They can measure PM10, PM2.5 and PM1.
These are non-equivalent instruments with an expanded uncertainty at the limit value for PM10 and PM2.5 assumed to exceed 25%.
Monitoring technique 4
Real-time monitoring.
Low-cost sensors use particle-counting by laser light scattering as the measurement principle.
Monitoring standard
There is no CEN, ISO, or BS standard method for this technique.
Volatile organic compounds (VOCs)
Here are the monitoring techniques and standards.
Monitoring technique 1
Periodic (average) sampling.
Sampling of VOCs by pumped (active) sampling onto sorbent tube, analysis by thermal desorption or capillary gas chromatography.
Monitoring standard
EN ISO 16017-1: Indoor, ambient and workplace air. Sampling and analysis of volatile organic compounds by sorbent tube or thermal desorption or capillary gas chromatography. Pumped sampling.
Part 1 of this standard for VOCs is appropriate for a wide range of compounds, including:
- hydrocarbons
- halogenated hydrocarbons
- esters
- glycol ethers
- ketones
- alcohols
The standard recommends several sorbents for the sampling of these VOCs, each sorbent having a different range of applicability. Very polar compounds will generally require derivatisation. Very low boiling compounds will only be partially retained by the sorbents, depending on ambient temperature, and can only be estimated qualitatively. Semi-volatile compounds will be fully retained by the sorbents but may only be partially recovered. The standard lists compounds that have been tested successfully using the standard. The standard may be applicable to compounds not listed, but in these cases, it is advisable to use a back-up tube containing the same or a stronger sorbent.
This standard is applicable to the measurement of airborne vapours of VOCs in a concentration range of approximately 0.5 µg/m3 to 100 mg/m3 per individual compound. The LOD in practice is dependent on detector noise and blank levels in analyte and sorbent tubes.
Monitoring technique 2
Periodic (average) sampling.
Sampling of VOCs by diffusive (passive) sampling onto sorbent tube; analysis by thermal desorption or capillary gas chromatography.
Monitoring standard
EN ISO 16017-2: Indoor, ambient and workplace air. Sampling and analysis of volatile organic compounds by sorbent tube or thermal desorption or capillary gas chromatography. Part 2: Diffusive sampling.
This standard is for the measurement of airborne vapours of VOCs. It has a mass concentration range of approximately 2 µg/m3 to 100 µg /m3 per individual organic compound for an exposure time of 8 h. It has a mass concentration range of approximately 2 µg/m3 to 300 µg/m3 per individual organic compound for an exposure time of 4 weeks.
Monitoring technique 3
Real-time monitoring (quasi-continuous).
Measurement of benzene, 1,3-butadiene, toluene, ethylbenzene, m- and p-xylenes, o-xylene, and other hydrocarbons by automatic pumped (active) sampling with in-situ analysis by gas chromatography.
Monitoring standard
EN 14662-3: 2015 Ambient air. Standard method for the measurement of benzene concentrations. Automated pumped sampling with in-situ gas chromatography.
Instrument manufacturers can extend MCERTS instrument-certification beyond benzene to include (but not limited to) the following:
In the C2-C6 group: ethane, ethene, propane, propene, iso-butane, n-butane, acetylene, trans-2-butene, 1-butene, cis-2-butene,2-methyl butane, n-pentane, 1-3 butadiene, trans-2-pentene, 1-pentene, 2-methyl pentane, n-hexane, isoprene
In the C6-C12 group: 2,2,4-trimethyl pentane, n-heptane, toluene, n-octane, ethyl benzene, m-xylene, p-xylene, o-xylene, 1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene and 1,2,3-trimethyl benzene.
Monitoring technique 4
Real-time monitoring (open path approach).
DOAS based open-path systems.
Monitoring standard
The relevant monitoring standard is EN 16253 Air quality. Atmospheric measurements near ground with active differential optical absorption spectroscopy (DOAS). Ambient air and diffuse emission measurements.
Monitoring technique 5
Real-time monitoring (open path approach).
FTIR based open-path systems.
Monitoring standard
The relevant monitoring standard is EN 15483: Ambient air quality. Atmospheric measurements near ground with FTIR spectroscopy.
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