6. Writing an odour management plan
Source: gov.uk (2025-12-03)

How to write an odour management plan for your permitted activity.

Your odour management plan (OMP) must describe the measures you will take to control odour pollution, including:
- any raw materials
- intermediate products
- processes
- releases
- containment
- abatement
- enhanced dispersion
- impact mitigation
Your OMP must include or refer to an assessment of the risks specific to your site.

Based on the risks you identify, your OMP must document the measures you will take to control odour pollution.

Your OMP must also identify:
- the auditable records you will keep
- any relevant performance standards
- monitoring you will do
- how you will interpret monitoring results
- how you will document your decisions
Any guidance you use to support the OMP must be current. You must include a reference, including date and version number, for any guidance you refer to in the OMP.

For all procedures, including decision making, you need to write these clearly:
- as unambiguous commitments
- with defined timescales which can be audited against
You must avoid tentative statements such as ‘may’ or ‘will consider’ or ‘if practicable’. These do not represent commitments.

When you mention supporting documents in the OMP, you need to clearly cross-reference these in the text, including a date and version number. You need to either:
- append supporting documents to your OMP
- submit them as separate supporting documents
Odour management at sites with a high potential for odour pollution can be a major challenge. OMPs for these sites need to be detailed and comprehensive.

Sites with a low odour potential may need comparatively simple and concise OMPs.

You can request an OMP template to help you include all the correct information. Email xxx@xxx.xx (mailto:xxx@xxx.xx).

Objectives

Your OMP must show your commitment to:
- understanding the risks of odour pollution caused by your activities
- using appropriate measures (or best available techniques (BAT)), including monitoring and contingencies, to control and minimise odour pollution
- preventing odour pollution, and only where that is not practicable, to minimise it
- always preventing serious pollution
- minimising the risk of odour releasing incidents or accidents by anticipating them and planning accordingly
- documenting odour control measures taken and the performance of those controls
Preparing a risk assessment

The guidance on risk assessments for your environmental permit (https://www.gov.uk/guidance/risk-assessments-for-your-environmental-permit) gives general advice on carrying out risk assessments for environmental impacts. This guidance explains 6 steps. Their relationship to odour is set out in more detail here.

Identify and consider risks for your site, and the sources of the risks

The underlying risk of odour pollution for any site will be the inventory of odorous and potentially odorous materials, whether in storage or being treated. These materials may be solids, liquids or gases, but you should not confuse them with emissions or discharge points. You need to have a thorough understanding of the materials and their odour potential for any risk assessment.

For some sites, such as landfills or rendering sites, holding large quantities of odorous materials is part of the process. However, there will still be measures you can take to minimise the odour concentration of these materials.

For other sites, the quantities of odorous materials being stored or treated will be one of the most important risk factors you need to control.

The amount of material a site can safely handle at one time (operational limit) is not determined by the official permit specified limit alone. Instead, the amount depends on practical factors, including the type of materials and how they are managed.

The nature of odours can strongly influence their risk of causing odour pollution. While perceptions can vary between individuals, odour from rotting meat will normally be perceived as more offensive than odour from aerobically composted garden waste.

You must also consider the risk of accidents which might result in odour pollution. This might include:
- spills or other material handling failures
- plant or equipment failure
- operational mistakes
- vandalism
- flooding
You should also consider any accident risks which might be specific to your activity, site or location.

Your risk assessment for abnormal operations must include all reasonable and relevant scenarios which are:
- common for the sector
- likely to occur at the site
Scenarios involving the emergency services may be important for other risk assessments. But you do not need to consider them when assessing potential odour pollution.

Identify the receptors at risk from your site

Receptors include people, animals, property and anything else that could be affected by a hazard.

For odour pollution, the receptors of concern are always people.

Your risk assessment should set out:
- the approximate number of people affected
- their relative sensitivities
- the relative exposure levels
Work this out based on the following distances from the site:
- landfill – 2km
- biowaste – 1.5km
- farming – 1km
- food – 1km
- waste treatment – 0.5km
These distances are based on experience and are for risk screening purposes, to help you consider potential receptors.

You may need to alter these distances after considering:
- any past odour pollution
- other relevant site-specific factors
The vulnerability of people to odour offence is strongly influenced by their personal circumstances. Some of these can be observed or inferred from local land uses. For example, people at home or in a pub garden may be resting or eating and are likely to be more sensitive than people working on an industrial estate or walking by.

Other vulnerabilities, such as pregnancy or health concerns, are often unknown and more difficult to predict from land uses. That is unless there are institutions which cater to those individuals, like a hospital or nursing home.

The sensitivity and number of people in the area can also change as land close to existing permitted sites is developed or repurposed. When this happens, you may need to adapt your risk assessment and associated control measures to reflect the new circumstances. New residents, visitors or users of repurposed properties must be protected from odour pollution in the same way as current occupants.

There can also be secondary impacts on businesses (holiday caravan parks), community institutions (sports clubs) or public events (a festival) if people avoid these locations due to unpleasant odours.

Identify the possible pathways from the sources of the risks to the receptors

Usually, odour exposure pathways involve:
- release from a solid or liquid to a vapour (gas)
- escape from any containment features
- dispersion in the atmosphere to an offsite receptor (people)
Understanding how these factors apply to your site and activities will help you understand any associated risks.

Releases of odorous chemicals from solids or liquids to vapours (gasses) will be influenced by:
- temperature
- chemical factors (pH)
- any air movement to carry vapours away
Containment features may be as simple as a static windrow of undisturbed compost, or as complex as an engineered structural containment system with ventilation to abatement.

You need to consider events when these containment measures will be routinely compromised (moving the compost or opening a door).

Containment measures may also be ineffective due to:
- engineering failures
- lack of effective maintenance
- poor management
- accidents
Intermittent releases can cause heightened levels of annoyance.

Poor atmospheric dispersion conditions can carry concentrated odorous emissions longer distances. For example:
- low wind speeds
- cold drainage (adiabatic or katabolic) flows
This can lead to more people being affected, with higher perceived intensities for longer.

Moderate to good atmospheric dispersion conditions (high turbulence) can lead to nearby receptors experiencing highly variable levels of exposure. As they detect peaks of odour concentration over very short time periods (every few seconds), this can increase their frequency of detection and perception of intensity.

Assess risks relevant to your specific activity and check they are acceptable and can be screened out

This step from the general risk assessment guidance is not relevant for odour pollution.

State what you will do to control risks if they are too high

The measures you will use to control the risk of odour pollution will be included in your OMP. With these measures, you will prevent odour pollution from your site. Or, when that’s not possible, minimise it.

Your risk assessment must conclude that your site is unlikely to cause serious odour pollution and that you are committed to preventing it. You must show that you understand the risks and are able to minimise them.

If your site has previously caused serious odour pollution, you must demonstrate that you know why. You must also show what changes you have made to prevent it from happening again.

Submit your risk assessment as part of your permit application

Your risk assessment will be assessed together with your OMP.

Management of odorous materials

The OMP should include an inventory of all potentially odorous solid, liquid and gaseous materials held on site:
- with descriptions, locations and quantities
- across the full range of normal operating conditions
Do not confuse the inventory of materials with emissions to atmosphere.

The inventory must identify limits on:
- material storage times
- quantities
- storage conditions
You should also specify how you will:
- effectively monitor all relevant parameters
- keep records on this monitoring
All your limits and methods must reflect appropriate measures for storage of materials, including those found in the Environment Agency’s general permitting and sector specific guidance.

Process controls

When you store, process or treat odorous or potentially odorous materials, your OMP must state the appropriate measures you will use to control or destroy odorous chemicals.

For example, maintaining aerobic conditions within composting materials. Process monitoring must reflect a thorough understanding of the process in question and include factors which could influence odorous releases.

Your monitoring must provide strong evidence that process controls are properly managed and working as intended.

If you use Supervisory Control and Data Acquisition (SCADA) systems to provide elements of process control and monitoring data, you must provide details of these systems.

Emissions to atmosphere

Management of emissions to atmosphere includes:
- reducing evaporation of odorous chemicals, when possible
- containing and abating these emissions, if needed
The OMP must describe or link to:
- the process
- containment and abatement systems
- emissions points
- fugitive emissions
- monitoring
- performance standards
- documentation of measures taken
Monitoring must provide good evidence that emissions are properly managed and that any control measures are working as intended.

For any controls or monitoring methods which are novel or not established in BAT conclusions, you must describe and justify these in line with the guidance on novel methods.

Engineering assessments

When appropriate, you must support the control measures specified in the OMP with professional engineering assessments. This is particularly important for large or complex processes or containment and abatement systems. You need to show that the assessments are relevant and sufficient by providing:
- the name of the professionals doing the assessment
- a summary of their qualifications
- an explanation as to how the qualifications are sufficient and relevant to the assessment
The Health and Safety Executive (HSE) has guidance on selecting ventilation solutions and identifying competent designers (https://www.hse.gov.uk/pubns/indg408.pdf).

Dispersion

The OMP must show that you have identified the potential for poor dispersion conditions, such as:
- low wind speeds
- cold drainage (adiabatic or katabolic) flows
Where appropriate, you must specify your short-term contingency odour controls.

You must justify any enhanced dispersion methods, such as elevated stacks, and quantify their expected benefits as much as possible.

Gaussian modelling may help you to understand the relative benefits of alternative odour dispersion measures, abatement methods and potential patterns of impacts on surrounding communities.

On site monitoring

All monitoring you specify in the OMP must clearly relate to enabling and assessing odour control.

You should keep complete monitoring records in a format that can be audited.

You must do appropriate monitoring to establish and demonstrate odour control procedures for every stage. This includes materials in storage, process controls, emissions, dispersion and impacts.

You must consider the interpretation of monitoring results in advance and associate with stated performance standards whenever possible.

Where appropriate, you must specify trigger values for contingency control measures.

You must clearly state the emission limits for channelled emissions and biofilters in the OMP, if these limits are not in the permit. Exceeding these limits will show that odour controls are not working to an appropriate standard and are not appropriate measures.

Odour incident reports

You may receive reports of odour pollution in the community near your site, either from the Environment Agency or the public.

Your OMP must specify how you will investigate odour complaints. This is something you must do promptly to work out if there are problems with any materials, process controls, containment or abatement methods. This is called a preliminary odour investigation procedure.

The OMP must also describe how you will document:
- the results of any odour complaint investigation
- any secondary investigations
You must make these details available to the Environment Agency on request.

Your OMP should also describe how you will document the remedial measures you will take.

The preliminary odour investigation procedure needs to be brief and focus on site activities. The results may lead to a more involved secondary investigation. The objective of these investigations is not to validate the odour reports. It is to clarify what was happening on site at the time which may have led to odour being released.

Odour incident response planning

Based on your odour risk assessment, you must consider what abnormal operating conditions, emergencies or other incidents might adversely affect the control of odour pollution.

You need to anticipate what could reasonably go wrong with:
- materials
- process controls
- containment or abatement systems
This includes reasonably foreseeable internal and external events, such as:
- operational mistakes
- extreme weather events (including droughts)
- local flooding
- equipment breakdowns
- transport delays
- staffing interruptions
Your OMP must specify:
- measures to reduce the likelihood of these incidents occurring
- how they will be quickly recognised if they do occur
- how their odour impacts will be minimised
- how the process will be brought back under control promptly
You should, wherever possible, plan to recognise problems through observations or monitoring the process. You need to identify and include clear criteria for starting further investigations or remedial actions, rather than wait for complaints.

You also need to describe your contingency plans for escalating the response to potentially serious out of control conditions. The Environment Agency recognises that odour management procedures will be of secondary importance for the duration of any incident involving emergency services (for example fire, police, ambulance).

Inspection, maintenance, and repairs

The ongoing performance of odour control measures will rely, in part, on the condition of infrastructure elements. These include:
- process equipment
- monitoring instruments
- ventilation systems
- buildings
- containment features
- abatement systems
Your OMP must specify (or refer to) an inspection schedule that aims to discover infrastructure faults in a timely way. These inspections must identify and record any faults noted. You should consider any relevant performance standards for equipment or other infrastructure. This must include any needed calibration of instruments used.

You must specify appropriate maintenance, in line with the manufacturer’s instructions, to maintain system performance.

You must keep records of maintenance measures and inspection findings in a format that can be audited and shared with the Environment Agency on request.

When inspections or maintenance indicate repairs are needed, you must record and promptly implement this.

If there’s a fault which results in serious odour pollution or an imminent risk of serious odour pollution, you must use secondary control measures. Where relevant, this should include stopping relevant site activities such as accepting waste.

Organisation

OMPs a part of your environmental management system. They must be practical operational documents which can be used effectively by relevant site staff.

OMPs which are poorly organised, vague, filled with superfluous material, or difficult to understand are not fit for purpose and are likely to be rejected.

You can request an OMP template to help you include all the correct information. Email xxx@xxx.xx (mailto:xxx@xxx.xx).

Review of OMPs

You must review your whole OMP at least once a year. This is so you can check if it:
- still applies to current site practices
- includes all appropriate measures
As part of this review, you must assess the performance of odour control measures, considering:
- odour pollution reports from all sources
- all relevant site monitoring
Your OMP must set out the review procedure, including:
- the frequency of review
- the member of staff who will perform the review
- a summary of any changes made as a result of the review
You must make these reviews available to the Environment Agency on request.

You must start a more focused review:
- any time site operations are expected to change
- when there’s a serious odour pollution event
If your permit requires you to have an OMP approved by the Environment Agency, then you need to submit any revised OMPs to them for review and approval. You may need to discuss proposed changes with them.

The Environment Agency may charge for OMP reviews in line with its charges guidance (https://www.gov.uk/guidance/environment-agency-fees-and-charges).

Go back to contents (https://www.gov.uk/guidance/odour-management-comply-with-your-environment-permit).