Environment Agency
1. Introduction
You must identify the aims and objectives of an ambient air quality monitoring survey and develop a monitoring strategy to make sure you meet these objectives. This document discusses the factors that you must consider when developing the monitoring strategy, with some suggested approaches to specific types of survey. It gives guidance on the handling, analysis, interpretation, and reporting of air quality monitoring data.
Five further ambient air monitoring guides give supplementary information to this strategy guide:
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Monitoring ambient air: quality control and quality assurance
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Monitoring ambient air: choosing a monitoring technique and method
The index of monitoring methods provides guidance on the monitoring methods available for assessing levels of different pollutants in the ambient atmosphere. It should enable you to choose an appropriate monitoring method or technique.
Your ambient air quality monitoring and assessments must have proper quality assurance and quality control procedures. You should have the necessary experience that shows your competence. Membership of a relevant professional body provides additional assurance.
2. Reasons for conducting ambient air quality monitoring
You may need to do ambient air quality monitoring:
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as a requirement of a permit issued under the Environmental Permitting Regulations (EPR)
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for compliance with legislation requiring monitoring of the ambient atmosphere, for example the Air Quality Standards Regulations 2010
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by local authorities reviewing air quality in their area as part of the Local Air Quality Management system required under The Environment Act 1995
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as part of an Environmental Statement or a stand-alone air quality assessment submitted in support of a planning application (or to inform other spatial planning decisions) under relevant planning regulations
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as a post-development planning condition to provide a continuing check on any environmental effects and the effectiveness of any mitigation measures proposed
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for investigative or research purposes, such as investigation of health effects, atmospheric chemistry, or atmospheric pollution dispersion
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for monitoring the extent of leaks of gas products such as methane
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for monitoring of greenhouse gas emissions on a voluntary basis or as part of the requirements of carbon offsetting schemes
There may be more specific aims and objectives for carrying out an ambient air quality survey, and you may adopt a variety of sampling schemes for monitoring the pollutants. For example, the monitoring of traffic pollution may focus on roadside air sampling, whereas the monitoring of ozone pollution is often carried out at rural sites. A monitoring survey may consist of:
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a national network of air quality monitoring stations
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a smaller network designed to monitor regional or local air quality
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an assessment of air quality around a specific site or source
To make sure your sampling programme is technically valid and cost- effective, you should define the objectives of the proposed study at the design stage. The aims of different studies may vary but may include one or more of the following:
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comparison of ambient air quality levels with standards, objectives, or Environmental Assessment Levels (EALs)
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establishing baseline levels before development of a new pollution source
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establishing baseline levels after commissioning of a new pollution source
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resolving the contribution of one plant or emission source from the background
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assessing the effectiveness of any abatement measures or control measures
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monitoring air pollutants crossing a site boundary
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monitoring nuisance effects, such as odour or dust
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responding to complaints
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verifying predicted ambient air quality levels, such as from modelling or chimney height calculations
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carrying out a survey using simple methods to decide if you need automatic monitors, and if so where you should be place them
3. The need for a monitoring strategy
You must design an air quality monitoring strategy so that it provides the most appropriate data to fulfil the aims and objectives of the survey. You must make decisions about:
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why do you need the monitoring
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what, where and when to sample
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how long to sample for
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how many samples to take and by what method
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quality assurance to make sure of appropriate results and to eliminate invalid data
Monitoring of common ambient pollutants is well established, with a range of automatic instrumental methods available, complemented by simpler manual methods. But the range of pollutants requiring measurement may be wide and may include many species where the measurement methods are not well developed.
4. Survey objectives and monitoring strategy
The data from a monitoring survey is normally used together with other investigative tools (for example, modelling, observations, complaints, compliance audits) to answer a particular question. For example:
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is the activity at the regulated site giving rise to nuisance impacts from dust at local residential dwellings?
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is the site activity giving rise to ambient particulate levels that exceed air quality standards?
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what is the flux (movement) of particulate matter across the perimeter of the regulated site?
These questions need different monitoring approaches. At a given site, more than one question may be relevant and so you may need several complementary monitoring approaches. This guidance describes how to design a monitoring strategy that aligns the monitoring survey with the aims and objectives of the study.
You must be clear on whether you want to measure the impact at receptors or the emission rate from the site boundary because they need different monitoring approaches. For example:
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if you want to quantify the impact at receptors, then monitor at the location of the receptors if the question is one of human health impacts, then it is usually appropriate to measure the concentrations of the pollutant
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if the issue is one of dust nuisance impacts, then measurement of deposition rates using a horizontally orientated collection gauge will be relevant (for example, total mass dust deposition rate by a Frisbee gauge)
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most monitoring at receptors is omni-directional you may need to also carry out directional monitoring if there are other significant local sources
If you want to quantify the emissions rate from the boundary of a regulated site, then you should monitor the rate at which the pollutant is crossing the site boundary at the perimeter of the site. For dust, the monitoring may be subjective observations of visual dust emissions or quantitative monitoring of dust flux using vertically orientated collection gauges.
What to consider when producing a monitoring strategy
What species to monitor
Once you have identified the target pollutant, you must decide in what form to monitor it. For example, total hydrocarbons or individual (speciated) hydrocarbons, total particulate matter or a specific size fraction.
When to sample and for how long
You must decide if sampling should be continuous or intermittent. You must consider:
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the averaging period of the relevant air quality standard or objective with which you will compare the data
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whether the impact is acute or chronic
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the temporal resolution required (for example, short peaks averaged over 3 minutes, 1-hour averages, daily averages)