What are they?

An emission is the release into the atmosphere of substances or forms of energy originating, directly or indirectly, from a source capable of causing air pollution.

Emissions may come from industrial processes, combustion, the storage and handling of substances, the use of solvents, treatment processes, internal transport, refrigeration systems and other activities carried out in workplaces.

Air pollution can affect both the environment and people’s health. Depending on their nature, concentration and duration of exposure, some pollutants can cause respiratory, cardiovascular and neurological effects, as well as cancer and reproductive effects.

The main air pollutants include:

1. suspended particulate matter, including PM10 and PM2.5;
2. nitrogen oxides (NOx);
3. sulphur dioxide (SO₂) and other sulphur compounds;
4. carbon monoxide and carbon dioxide (CO and CO₂);
5. volatile organic compounds (VOCs);
6. ground-level ozone, which can form in the atmosphere from other pollutants;
7. metals and their compounds;
8. polycyclic aromatic hydrocarbons (PAHs);
9. persistent organic substances;
10. halogens and their compounds;
11. certain substances that may affect the ozone layer or contribute to climate change.

Some emissions can have a direct effect on workers when they are generated or released inside the workplace. For example, a gas leak, the release of solvent vapours, or the generation of fumes and particles during a process may result in inhalation exposure.

Point-source and diffuse emissions

At workplaces, emissions can generally be divided into:

Point-source or channelled emissions: these occur through a defined emission point, such as a chimney, duct or extraction system. Such emissions may be subject to controls, measurements and limits established by the applicable legislation.

Diffuse emissions: these do not occur through a defined emission point. They may result from leaks, evaporation, storage, loading and unloading, handling of substances, spills, open processes or losses from equipment and installations. They can be more difficult to control.

It is important to distinguish between emissions released into the external environment and emissions that may cause exposure inside the workplace. An installation may comply with its environmental obligations while workers may nevertheless be at risk if hazardous concentrations of pollutants occur in the workplace air.

Occupational health and safety legislation requires risks arising from exposure to chemical agents at work to be assessed and controlled.

What can be done?

Workers and their representatives should be able to know which pollutants are emitted by the company, where they come from and what measures are in place to prevent or reduce emissions and exposure.

It is advisable to:

1. Identify the activities, processes and installations that generate emissions.
2. Find out which substances are emitted and in what quantities.
3. Identify both point sources and sources of diffuse emissions.
4. Check whether emissions may result in workers being exposed inside the installations.
5. Request that risks arising from emissions of chemical agents are included in the occupational risk assessment.
6. Check that any necessary environmental and workplace measurements are carried out appropriately and that the results are made available to workers and their representatives.
7. Pay particular attention to substances that are carcinogenic, mutagenic, toxic for reproduction, sensitising or otherwise seriously harmful to health.
8. Give priority to the elimination or substitution of hazardous substances whenever technically feasible. ISTAS identifies substitution as one of the main measures for eliminating chemical risks.
9. Give priority to prevention and control measures at source rather than relying exclusively on personal protective equipment.
10. Check the operation and maintenance of local exhaust ventilation, capture and abatement systems.
11. Pay particular attention to leaks and diffuse emissions, which may go unnoticed because they do not have a defined emission point.
12. Be familiar with procedures for dealing with breakdowns, leaks, spills and other accidental situations.
13. Check how waste and materials retained by filtration or abatement systems are managed, as they may contain high concentrations of pollutants.
14. Request information on the permits, notifications, controls and emission records applicable to the installation.
15. Participate, through workers’ legal representatives, in proposals to reduce emissions and exposure.

Where an activity is included in the Catalogue of Activities Potentially Polluting the Atmosphere (CAPCA), the applicable administrative and control requirements should be checked. Royal Decree 100/2011 establishes the catalogue and covers activities involving both point-source and diffuse emissions.

Certain industrial installations may also be subject to requirements arising from legislation on integrated pollution prevention and control, including integrated environmental permits and measures associated with best available techniques (BAT).

Action guides

1. Guide to waste-water discharge control and management. ISTAS, 2005.
2. Guide for the substitution of hazardous substances in companies. Practical manual for intervention. ISTAS.
3. Prevention of chemical risks in the workplace. Guide for intervention.
4. Risk elimination. Substitution. ISTAS. Updated material on the application of substitution as a preventive measure against chemical risks.
5. Guides and technical documents from INSST on chemical agents and the prevention of occupational exposure.

Classification

Emissions can be classified according to the pollutants released. The main groups of interest include:

1. Sulphur oxides and other sulphur compounds.
2. Nitrogen oxides and other nitrogen compounds.
3. Carbon monoxide and carbon dioxide and other carbon compounds.
4. Particulate matter, including PM10 and PM2.5.
5. Volatile organic compounds (VOCs).
6. Polycyclic aromatic hydrocarbons (PAHs).
7. Persistent organic substances.
8. Metals and their compounds.
9. Asbestos and other mineral fibres or hazardous particles.
10. Halogens and their compounds.
11. Cyanides.
12. Dioxins and furans.
13. Substances with carcinogenic, mutagenic or toxic-for-reproduction properties when they may be released into the air.
14. Ozone-depleting substances.
15. Fluorinated greenhouse gases.

The specific identification of pollutants must be based on the processes, raw materials, fuels, products used and operating conditions of each installation.

Legislation

Air quality and atmospheric protection

1. Law 34/2007, of 15 November, on air quality and protection of the atmosphere. This is the main Spanish legislative framework for the prevention, monitoring and reduction of air pollution. Its consolidated text incorporates subsequent amendments and was last updated on 4 December 2025.
2. Royal Decree 100/2011, of 28 January, updating the Catalogue of Activities Potentially Polluting the Atmosphere (CAPCA) and establishing the basic provisions for its application.
3. Royal Decree 102/2011, of 28 January, on the improvement of air quality, establishing air-quality objectives and assessment criteria.

Industrial emissions

1. Royal Legislative Decree 1/2016, of 16 December, approving the consolidated text of the Law on integrated pollution prevention and control.
2. Royal Decree 815/2013, of 18 October, approving the Regulation on industrial emissions and implementing legislation on integrated pollution prevention and control. Its consolidated text incorporates subsequent amendments.
3. Directive (EU) 2024/1785, amending Directive 2010/75/EU on industrial emissions. It should be taken into account when monitoring developments in European legislation and its transposition into Spanish law.

Volatile organic compounds

1. Royal Decree 117/2003, of 31 January, on the limitation of emissions of volatile organic compounds due to the use of solvents in certain activities.

Risks to workers

1. Royal Decree 374/2001, of 6 April, on the protection of workers’ health and safety against risks related to chemical agents at work.

Fluorinated gases and substances affecting the ozone layer

1. Regulation (EU) 2024/573, on fluorinated greenhouse gases, which repealed Regulation (EU) No 517/2014. It regulates, among other matters, containment and prevention of emissions, recovery, use and certain prohibitions.

References

Last updated: August 2026.