Meeting occupational exposure limits: How air filtration lowers exposure in the workplace
In non-residential buildings, workplace air quality is moving back into focus: the recast EU Energy Performance of Buildings Directive (EPBD) treats energy efficiency and indoor climate within a single framework.1 In parallel, the updated EN 16798-3:2025 standard for ventilation and air conditioning systems in non-residential buildings now explicitly covers molecular contaminants alongside particles.2
In industrial manufacturing, the question of combined protective measures against a wide range of airborne contaminants has been on the table for a long time, independently of any single new regulation: oil mist, dust and noxious gases, for example, are generated directly by the process. How much of them is permissible is set by occupational exposure limits for hazardous substances – and those limits differ from country to country.
For planners and operators, both paths lead to the same task: selecting the right filtration, sizing it correctly and monitoring it continuously – so that occupational health protection, cleaner air, energy efficiency and life cycle costs come together as a single package.
OEL, WEL and AGW: What the terms actually mean
An occupational exposure limit – in Germany, the Arbeitsplatzgrenzwert (AGW) – states the concentration of a substance in workplace air up to which acute or chronic damage to health is generally not expected. In Germany, for example, these values are listed in the Technical Rule for Hazardous Substances TRGS 900. They apply as eight-hour shift averages and are made binding by the German Hazardous Substances Ordinance.
A national example: for dusts with no specific toxic effect, the general dust limit under TRGS 900 applies: 1.25 mg/m³ for the respirable A fraction and 10 mg/m³ for the inhalable E fraction.3
Internationally, several designations are in circulation. Occupational Exposure Limits (OELs) is the umbrella term for limits on work-related exposure; in the United Kingdom they are called Workplace Exposure Limits (WELs). In the United States, the legally enforceable Permissible Exposure Limit (PEL) set by OSHA applies, complemented by the Recommended Exposure Limit (REL) issued by the research institute NIOSH. In each case, only the government-set value is binding; recommendations such as the REL or the German MAK value (maximum workplace concentration) serve as orientation for workplace exposure standards.
Just how far apart these values can be is clear from oil mist produced by mineral-based lubricants: OSHA cites 5 mg/m³ as an eight-hour average, while NIOSH recommends 0.4 mg/m³ for the thoracic fraction of metalworking fluid aerosols.4 Companies that manufacture internationally therefore check site by site which regional occupational exposure limits apply.
What contaminants occur in the workplace?
Which filtration makes sense depends on what is actually loading the air – and workplace contamination differs fundamentally between a production hall and an office building.
Industrial manufacturing: Oil mist, emulsion mist and process emissions
In machining, oil mist is generated right at the workstation. And it is not just oil: depending on the metalworking fluid and the process, the aerosol also contains additives, fine metal particles, bacteria and spores. Grinding, hardening and plastics processing add thermally generated fumes.
Left untreated, that mist affects more than measurable industrial workplace exposure: oil settles on floors, machines and workpieces. The result is not only extra cleaning work but also a slipping hazard for employees – in other words, a direct risk to safety on the production floor.
Non-residential buildings: Particulate matter, ozone, nitrogen oxides and volatile organic compounds
In office buildings, schools and public administration buildings, but also in hospitals and life sciences environments, the pattern is a different one: a large share of the load enters the building with the outdoor air, while further substances are generated indoors – not by manufacturing processes, but by building products, furniture, cleaning agents or printers, for example.
The relevant fractions here are PM10 (particles < 10 µm) and PM2.5 (< 2.5 µm), and increasingly ultrafine particles (< 0.1 µm), which fall under workplace limits for particulate matter. Added to these are gaseous pollutants such as ozone, nitrogen oxides, sulfur dioxide (SO2) and volatile organic compounds (VOCs), including formaldehyde. For indoor air in offices, occupational exposure limits are usually not the governing benchmark; the guideline values issued by the German Committee on Indoor Guide Values apply instead – and they, too, belong in the risk assessment for office workplaces.
A common misconception concerns the occupational exposure limit for carbon dioxide: the CO₂ level in room air is an indicator of ventilation performance, not of filter performance. It falls with a sufficient supply of outdoor air, not with a finer filter. Filtration and air exchange are two separate levers.
To put that in perspective: People in Europe spend an average of around 90 percent of their time indoors.5 The World Health Organization (WHO) recommends an annual mean of 5 µg/m³ for PM2.5 and 10 µg/m³ for nitrogen dioxide.6 From 2030, the EU Air Quality Directive sets values of 10 and 20 µg/m³ respectively.7 So even where European requirements are met, outdoor air is not free of pollution – the European Air Quality Index shows how high current levels are.8
From regulation to action: Risk assessment and the STOP principle
Filtration technology is always part of a comprehensive protection concept, never the sole means of meeting an AGW (or WEL or OEL). Take Germany as an example: the legal framework for the full set of measures against hazardous substances in the workplace is formed by the Occupational Safety and Health Act, the Hazardous Substances Ordinance and the supplementary Occupational Safety Act, made concrete by the Technical Rules for Hazardous Substances (TRGS) and the DGUV regulations. Depending on the sector or industry, further occupational safety regulations may apply. The starting point is always the risk assessment: employers determine which hazardous substances occur, how high exposure is and which occupational safety rules apply.
The order of priority follows the STOP principle: substitution before engineering measures, engineering before administrative measures, and administrative before personal protective measures. Personal protective equipment (PPE) – respiratory protection when handling chemicals, say, or PPE for hazardous substances – deliberately comes last: it protects individual employees, but it does not change the load in the room. Extraction and filtration lower the concentration for everyone working in the area.
For ventilation and air conditioning systems, EN 16798-3:2025 spells out the requirements, and Eurovent recommendations 4/21, 4/23 and 4/26 provide guidance on energy evaluation and filter selection.9 One important qualification: These are recommendations from industry experts that are consulted as one basis for legal assessment in the event of a legal dispute. Guidelines or recommendations compiled by experts therefore carry legal weight comparable to that of standards or certificates. Inspection, cleaning and filter changes are also covered by VDI 6022 – the reference point for hygiene in air handling systems.
Choosing and sizing the right filtration technology
Installing a filter is not enough. In practice, we often see systems that are undersized or that use the wrong technology – and separation efficiency then falls short of expectations. There is no one-size-fits-all solution: technology and sizing depend on the location, the contaminant, the process and the workplace air quality you are aiming for.
The filtration triangle: Balancing efficiency, pressure drop and service life
Higher separation efficiency is not automatically the better solution. Three variables are interlinked and form what Frank Spehl calls the filtration triangle: filtration efficiency, differential pressure and service life. A finer filter offers higher filtration efficiency, but it usually also increases pressure drop and with it the fan's energy demand; depending on the filter medium, service life is shortened as well.
The goal, then, is not the finest filter but the right one: it removes what needs to be removed without creating additional energy demand or maintenance effort. That rule holds in industry as it does in buildings – everywhere an adequately clean and safe environment is the objective.
For air handling systems, the perfect balance is also a business decision: energy consumption in operation accounts for a substantial share of an air filter's total cost over its service life.
Eurovent recommendation 4/21 provides a method for evaluating energy performance, and the resulting energy classification ranges from A+ to E.
Monitoring: Demonstrating filtration performance over time
Filter selection determines initial performance; operation determines the sustained effect. The established measurement variable is differential pressure: it indicates the loading of a particle filter and enables condition-based maintenance planning – in air handling systems just as in our ScandMist systems.
On industrial systems, we also measure on site: determining the load upstream and downstream of the filter system shows how effective separation actually is and whether the applicable requirements are being met.
For molecular pollutants such as VOCs and ozone, monitoring workplace limits is technically possible, but more demanding than for particle filters. Operators therefore often work with defined service lives and regular checks of the kind set out in VDI 6022.
More than meeting limit values
Well-matched filtration delivers benefits that reach well beyond limit values alone. Effective oil mist separation reduces deposits in production and the slipping hazards that come with them, and the separated oil can be returned to the process. In buildings, the right filter combination improves air quality where people spend most of their working day – an important factor for productivity, general well-being and focus.
That makes filtration a building block for employee health, manufacturing safety and resource-efficient operation – provided it is designed for the actual exposure situation. One important point: our filtration solutions help reduce pollutant loads and create the required conditions. On its own, filtration can only ever support compliance with occupational exposure limits, never guarantee it.
MANN+HUMMEL: We deliver cleaner air and greater safety in the workplace
Whether it is filtration solutions for ventilation and air conditioning systems in non-residential buildings or for oil mist at the machine tool, we cover both tasks from a single source.
MANN+HUMMEL Air Filtration is responsible for particle and molecular filtration to ensure the best possible indoor air quality – from facility management and microelectronics & optics to healthcare, laboratory & pharma and the food industry. For building filtration alone, our portfolio ranges from coarse and fine dust filters to HEPA filters and on to activated carbon and molecular filters. So you can put together the right filter combination without switching suppliers. One standout: We offer the most A+ and A certified filters (per Eurovent 4/21) on the market – an important decision criterion for energy-conscious decision-makers.
MANN+HUMMEL Original Equipment covers industrial applications right through to oil mist separation in machining.
Would you like to know whether your existing filtration matches your contaminants and your application? Or are you planning a new system and want separation efficiency, energy demand and service life to work together from the outset? Talk to our experts.
1 European Parliament and Council of the European Union. Directive (EU) 2024/1275 on the energy performance of buildings (EPBD): Directive - EU - 2024/1275 - EN - EUR-Lex
2 European Committee for Standardization (CEN). EN 16798-3:2025, Energy performance of buildings – Ventilation for buildings – Part 3: For non-residential buildings: BS EN 16798-3 - 2025-06-23 - DIN Media
3 German Social Accident Insurance (DGUV). General dust limit value (ASGW) under TRGS 900: FA GK: neue TRGS 900. TRGS 900 can be viewed here: BAuA - Regelwerk - TRGS 900 Arbeitsplatzgrenzwerte - Bundesanstalt für Arbeitsschutz und Arbeitsmedizin
4 Occupational Safety and Health Administration (OSHA). Metalworking Fluids: Safety and Health Best Practices Manual: Metalworking Fluids - Metalworking Fluids: Safety and Health Best Practices Manual | Occupational Safety and Health Administration
5 European Agency for Safety and Health at Work (EU-OSHA). Indoor air quality (IAQ): Indoor air quality (IAQ) - OSHwiki | European Agency for Safety and Health at Work
6 World Health Organization (WHO). WHO global air quality guidelines: particulate matter (PM2.5 and PM10), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide: WHO global air quality guidelines: particulate matter (PM2.5 and PM10), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide
7 European Parliament and Council of the European Union. Directive (EU) 2024/2881 on ambient air quality and cleaner air for Europe: Directive - EU - 2024/2881 - EN - EUR-Lex
8 European Environment Agency (EEA). European Air Quality Index: European Air Quality Index
9 Eurovent. Eurovent 4/21 – Energy Efficiency Evaluation of Air Filters (2019); Eurovent 4/23 – Selection of EN ISO 16890 rated air filter classes (2022); Eurovent 4/26 – Selection of Molecular Filters (2025):
Occupational exposure limits: Key questions and answers
There are plenty of questions around OELs and workplace air quality. We have answered the most important ones.
Occupational exposure limits, or OELs, is an umbrella term for limits that describe the permissible exposure of employees to hazardous substances. Germany's Arbeitsplatzgrenzwert (AGW) and the British Workplace Exposure Limit (WEL) are examples of how the principle is expressed at national level.
An occupational exposure limit – in Germany, the Arbeitsplatzgrenzwert (AGW) – states the concentration of a hazardous substance in workplace air up to which acute or chronic damage to health is generally not expected. In Germany, these values are listed in TRGS 900 and made binding by the Hazardous Substances Ordinance.
The values are set by government bodies and expert committees. In Germany, for example, the Committee on Hazardous Substances publishes the OELs in TRGS 900; in the United States, OSHA does so. They are based on toxicological and occupational medicine data as well as epidemiological studies. Scientific bodies such as the Senate Commission of the German Research Foundation (MAK values) or NIOSH additionally derive recommended exposure limits.
The values set by the government are enforceable: in Germany, the Arbeitsplatzgrenzwert under TRGS 900 in conjunction with the Hazardous Substances Ordinance; in the United States, OSHA's Permissible Exposure Limit (PEL). Values such as the MAK value or NIOSH's Recommended Exposure Limit (REL) are expert recommendations without direct legal force.
Mass concentrations in mg/m³ are common, or – for gases and vapors – volume fractions in ml/m³ (ppm). The reference is usually an eight-hour shift average. Short-term values for exposure peaks and an excursion factor may be specified in addition.
Employees and companies do not calculate limit values; they compare measured exposure against the specified value. To do so, the pollutant concentration over the shift is time-weighted, averaged and then set against the shift average. Molar mass and molar volume under standardized conditions are used to convert between mg/m³ and ppm.
Responsibility lies with the employer. As part of the risk assessment, the employer determines exposure, defines protective measures and verifies that they work. Occupational safety specialists and company physicians provide support; government occupational safety authorities and the accident insurance institutions provide oversight.
Through a combination of measurement and measures: determine exposure, enclose or extract pollutant sources wherever possible, size suitable filtration and monitor its performance in operation – via differential pressure, for example, or through measurements upstream and downstream of the filter system. Well-sized filtration can significantly reduce the load in the air and support companies in meeting applicable requirements.
The STOP principle is the guide: first substitution of the hazardous substance, then engineering measures such as enclosure, extraction and filtration, followed by administrative measures and, last of all, personal protective equipment (PPE). Engineering measures work for everyone in the area and therefore take precedence over PPE.
