Odour emissions represent a technical and regulatory issue of major importance for companies, industrial plants, and environmental sector operators. Any activity that handles organic waste, wastewater, biomass, food products, or chemical substances can generate odours that may affect air quality and the well-being of exposed individuals. This can lead to complaints, regulatory requirements, and, in more critical cases, legal disputes.
In recent years, the regulatory framework, both in Italy and at the European level, has evolved significantly, recognizing odours as a relevant parameter of environmental impact and introducing increasingly structured technical and management tools for their assessment and control. In Italy, in particular, the introduction of Article 272-bis of D.Lgs. 152/2006 has provided for the possibility of adopting measures to prevent and limit odour emissions through regional regulations and environmental permits, supported by national technical guidelines.
This article analyzes the regulatory framework in Italy and Europe, the main technologies and monitoring systems for odour emissions (dynamic olfactometry, electronic sensors, and chemical analysis), practical applications across different industrial contexts, and future perspectives for regulatory and technological development.
Introduction to odour emissions
Odour emissions are substances released into the atmosphere, either channelled or diffuse, composed of elements capable of generating olfactory perceptions, even at concentrations below the toxicological thresholds established by environmental regulations on odours. These are complex mixtures of volatile organic compounds (VOCs) and other inorganic compounds. VOCs include oxygenated compounds and volatile hydrocarbons, while the most relevant inorganic compounds include sulphur- and nitrogen-based compounds. The composition of odour emissions can vary significantly depending on the production process, operating conditions, and meteorological conditions.
Impacts on health and air quality
The main impacts of odour emissions occur on multiple levels.
From a public health perspective, prolonged exposure to intense odours can cause disturbances such as sleep disruption, headaches, stress, and a general reduction in quality of life, even when the substances involved do not exceed regulatory toxicological thresholds.
Regarding air quality, the presence of odours often indicates a broader emission scenario, which may include both odorous and non-odorous substances with potentially significant environmental impact. The impact of an odour depends not only on its concentration but also on its nuisance potential, which is assessed by considering frequency, intensity, duration, and exposure context. Odour is considered an environmental variable useful for identifying environmental pressures and supporting the detection of critical issues or process anomalies, as highlighted by the National System for Environmental Protection (SNPA).
Finally, from an environmental protection standpoint, the uncontrolled dispersion of odours can compromise the relationship between industrial plants and local communities, especially near sensitive receptors.
Role of monitoring and regulatory compliance
For companies, monitoring odour emissions and ensuring regulatory compliance are strategic tools for environmental odour management. They help meet permit requirements (AIA, AUA), prevent complaints, and demonstrate a responsible approach, which is increasingly relevant also within ESG frameworks.
Regulations on odour emissions
Italian regulatory framework
In Italy, the regulation of odour emissions is set out in Article 272-bis of D.Lgs. 152/2006, the main reference text for air protection and emission reduction. The decree assigns a central role to Regions, which may define specific criteria, limits, and control methods through regional regulations and guidelines.
Some regions, such as Lombardy, Liguria, Piedmont, Emilia-Romagna, Friuli Venezia Giulia, and the Autonomous Province of Trento, have adopted specific guidelines for managing odour emissions, defining assessment methodologies and reference criteria for estimating odour impact. In some cases (Puglia and Basilicata), odour control is governed by regional law, while other regions rely mainly on the general principles of the national decree, supplemented by technical documents provided by ARPA and SNPA.
Companies subject to regulation must carry out odour impact studies and assessments, implement monitoring measures for industrial odour emissions, adopt containment and abatement systems, and undergo periodic inspections by competent authorities. Where integrated permits are required, such as the Integrated Environmental Authorization (AIA) or the Single Environmental Authorization (AUA), odour-related requirements may be explicitly included among the operational conditions to be complied with and regularly monitored.
Failure to comply may result in administrative sanctions and operational restrictions, as well as negative impacts on relationships with local communities. Complaints from citizens or inspections by ARPA may trigger verification procedures, potentially leading to additional requirements or, in more serious cases, temporary suspension of operations.
European regulations and comparison with Italy
At the European level, odour emission management falls within EU policies on air quality and integrated pollution prevention and control, particularly under the Industrial Emissions Directive (IED). A key reference is the Best Available Techniques (BAT), described in the Best Available Techniques Reference Documents (BREF), which provide technical guidance for various industrial sectors such as waste treatment, livestock farming, and the chemical industry, including odour management and control.
Unlike other air pollutants, for which binding limit values exist at EU level, odour emissions are not yet regulated by a specific directive. As a result, Member States have adopted different approaches, with varying levels of regulation. Countries such as Germany and the Netherlands use quantitative methodologies based on olfactometry and dispersion modelling to assess odour impact, expressing acceptability thresholds in European odour units per cubic metre (ouE/m³). The comparison with Italy highlights the importance of progressive regulatory harmonization, also to make industrial odour monitoring data comparable across regions and countries.
The main shared technical reference at European level is the UNI EN 13725:2022 standard, which defines the method for measuring odour concentration through dynamic olfactometry. This standard is widely cited in Italian regional guidelines and forms the methodological basis for official assessments.
Odour emission monitoring systems
Main technologies
The control of odour emissions is based on the integration of different technologies, each with specific characteristics, applications, and limitations.
Dynamic olfactometry
Dynamic olfactometry, defined by UNI EN 13725:2022, determines odour concentration through a panel of trained assessors. It is widely used for official assessments, permitting procedures, and precise characterization of emission sources. Results are expressed in European odour units per cubic metre (ouE/m³), enabling standardized comparisons. However, it provides discontinuous measurements and is not suitable for continuous monitoring.
Electronic odour sensors (e-nose)
Electronic odour sensors (IOMS – Instrumental Odour Monitoring Systems), commonly referred to as e-noses and regulated by UNI 11761:2023, enable continuous monitoring and recognition of specific odour profiles through arrays of chemical sensors and signal processing algorithms. These systems are particularly useful for real-time process control, plant operation management, and correlating emission events with odour complaints. Compared to olfactometry, they provide broader temporal coverage but require periodic calibration and site-specific training.
Chemical analysis of odours
Chemical analysis of odours uses techniques such as gas chromatography–mass spectrometry (GC-MS) and sampling with polymer bags (e.g., Tedlar) or canisters (e.g., SUMMA) to identify and quantify odour-causing compounds such as sulphur compounds, ammonia, and VOCs. These analyses are essential for defining effective mitigation strategies and correlating chemical composition of emissions with olfactory perception observed in the surrounding area.
Environmental contexts
Odour monitoring is applied across many sectors, each characterized by different emission sources and operational challenges.
Odour emissions in treatment processes
In the food industry, especially in meat, fish, oil, and by-product processing, odour emissions are often associated with processes such as cooking, fermentation, and the storage of raw materials.
In wastewater treatment plants, the main contributors to odour impact are sulphur compounds, such as hydrogen sulphide (H₂S) and mercaptans, and nitrogen compounds, such as ammonia (NH₃), with marked seasonal and operational variability.
In composting and waste treatment plants, odour management is essential for permitting, requiring capture and treatment systems (e.g., biofiltration) and continuous monitoring programs.
Odour emissions in the agricultural sector and territorial impact
In intensive livestock farming, ammonia and sulphur compounds are the main sources of odour impact on surrounding areas, with significant environmental, regulatory, and social implications.
In all these contexts, monitoring is crucial to prevent odour nuisance and maintain communication with regulatory authorities. Integrating measurement data with atmospheric dispersion modelling allows for a more comprehensive assessment of territorial impact, estimation of odour dispersion areas, and support for effective mitigation planning.
Future perspectives on odour emission monitoring
Future developments in the odour emissions sector are linked to both technological progress and ongoing regulatory updates at national and European levels.
From a technological perspective, odour monitoring systems are becoming more precise and integrated. Next-generation sensors offer improved stability, lower costs, and connectivity with digital platforms for centralized data management. Integration with artificial intelligence and machine learning opens new opportunities for automatic classification of odour profiles and prediction of emission events based on meteorological conditions.
Regulatory evolution and european alignment
On the regulatory side, there is increasing effort toward harmonizing odour emission regulations both across Italian regions and among European countries. Updates to air quality policies and BAT guidelines are gradually introducing more structured references to odour management at EU level, aligning the European framework with standards already adopted in countries such as Germany and the Netherlands.
In this context, dispersion modelling is becoming increasingly important as a technical tool supporting permitting assessments and mitigation planning.
Implications for companies and management strategies
For companies, investing in reliable and compliant odour emission control systems is not only an obligation but also a real opportunity to improve environmental performance.
The integration of monitoring systems, dispersion models, and digital data platforms enables companies to anticipate future requirements, optimize mitigation strategies, and strengthen relationships with local communities, reducing the risk of odour nuisance and legal disputes.
