Belgium regulates the air inside its buildings through four separate frameworks, each written by a different authority for a different slice of the building stock. The Codex on Well-being at Work sets binding air quality obligations for every employer with workers in Belgium. The federal indoor air quality law of 2022 does the same for operators of enclosed spaces open to the public. The regional EPB/PEB codes govern how ventilation systems are designed and installed when a building goes up or gets renovated. And an EU directive sets the limits for the outdoor air all of them draw from.
Three of the four create obligations for building operators. The fourth governs what the atmosphere may contain, a responsibility that sits with government rather than building owners, but which determines the baseline every building has to work with.
This guide follows the air in the order it travels: in from the outdoor atmosphere, through the system that filters and distributes it, and into the rooms where people sit.
The air outside: the EU Ambient Air Quality Directive (2024/2881)
Start here, because everything downstream inherits whatever is in the atmosphere at the air intake. The revised EU Ambient Air Quality Directive (2024/2881) was adopted on 23 October 2024, entered into force on 10 December 2024, and replaces the two previous EU directives that had governed outdoor air for close to two decades.
The annual PM₂.₅ limit – fine particulate small enough to pass through the lungs into the bloodstream – drops from 25 µg/m³ to 10 µg/m³, which lands between the old EU standard and the World Health Organisation’s 5 µg/m³ guideline. In 2024, 61% of EU monitoring stations already read at or below that 10 µg/m³ level, leaving 39% that did not, according to the EEA’s 2026 Air Quality Status Report. The PM₁₀ limit for coarser particles halves from 40 µg/m³ to 20 µg/m³, and the NO₂ limit, driven mostly by vehicle exhaust and combustion, halves as well. These become legally binding on 1 January 2030.
Meeting those ceilings falls to member states and regulators responsible for ambient air, alongside traffic policy and industrial permitting, several steps upstream of buildings. For building operators, the practical news is quietly favourable: the air showing up at the intake is about to get cleaner across the decade.
That relief only arrives in 2030, though. Until then, the outdoor air a building draws from still carries what it carries – vehicle exhaust along the E40 corridor and major intersections; industrial emissions across the Antwerp port zone; residential wood burning every winter. Whatever’s in the air when it reaches the intake is what the building’s own systems have to deal with, and that’s where the next three frameworks pick up.
To learn more, check out our 2024 post about the EU AAQ Directive 2024/2881.
Bringing the air indoors: EPB/PEB regional regulations and the recast EPBD
Once the outdoor air is established, the next framework governs how a building’s ventilation system pulls it indoors. In Belgium, the system is specified at the point of construction or major renovation by regional energy-performance codes, and it is being reshaped right now by an overdue EU directive that the whole bloc has failed to transpose on time (at the time of writing).
The rules in force now: EPB/PEB
Building energy performance is a regional competence, run by three administrations: VEKA in Flanders, Brussels Environment in the Brussels-Capital Region, and SPW Énergie in Wallonia. The regulations carry different names – EPB in Flanders, PEB in Wallonia and Brussels – and perform the same job, which is to govern the energy and indoor-climate performance of a building whenever a permit is required. Build an apartment block, renovate an office floor, convert a warehouse into lofts, and the EPB/PEB framework prescribes, among much else, which ventilation system goes in and what airflow it has to move. Those ventilation rules form part of the EPB/PEB certificate, and without a compliant certificate a property cannot legally be sold or let.
For residential buildings, the airflow rates come from the Belgian standard NBN D50-001, first published in 1991 and kept current through EPB annexes, which sets minimums room by room. Every habitable room needs 3.6 m³ of fresh air per hour for each square metre of floor, so a 30 m² living room needs at least 108 m³/h of supply. Kitchens, bathrooms and laundry rooms need at least 50 m³/h of extraction each; toilets need 25 m³/h. These are design-stage minimums whose installed performance has to be measured and documented before certificates are issued.
How the air gets moved matters, because the standard sorts ventilation into four types.
- System A runs on natural ventilation alone, open windows and passive façade vents with no fans, which is how most pre-war Belgian housing breathes and depends on wind pressure and temperature difference to shift air it cannot control.
- System B pushes air in with a fan and lets natural pressure pull it out, an awkward configuration to balance and rarely chosen.
- System C, the workhorse of Belgian new builds, draws air supply through adjustable grilles in the exterior walls and extracts stale air from the wet rooms through a central fan.
- System D, is mechanical on both sides, supply and exhaust driven by fans and usually fitted with a heat-recovery unit that reclaims warmth from the outgoing air.
The EPB/PEB standard still describes all four, but the airflow rates demanded now are too high and too precise for passive systems to deliver reliably, which has pushed Systems A and B out of new construction and left the real choice between C and D. System C is simpler to build and thus, cheaper; System D costs more upfront, recovers energy, and gives the designer tighter control over where the air goes. Out of the various systems, System D is the most commonly chosen option for new builds to meet stringent energy and airtightness requirements.
For non-residential buildings — offices, schools, healthcare, retail — the framework references a different set of standards, led by EN 16798-1:2019, which replaced EN 15251 and absorbed the ventilation-rate guidance formerly in EN 13779. The rates there follow the intended use of each room, its expected occupancy, and the target indoor-air-quality category, so a classroom holding 25 students carries a far higher per-person airflow requirement than a single-occupant office, and a hospital isolation room is different again. The designer picks the category per space, calculates airflow, and sizes the system, which makes non-residential ventilation bespoke room by room rather than a flat formula per square metre.
What’s changing: the recast EPBD
The EU Energy Performance of Buildings Directive was recast in 2024 as Directive (EU) 2024/1275, and it directly changes what the regional EPB/PEB codes have to contain. The transposition deadline was 29 May 2026, which every one of the 27 member states missed. On 15 July 2026 the European Commission opened infringement proceedings against all 27, issuing letters of formal notice that gave each country two months to respond and finish transposing, with reasoned opinions and ultimately daily financial penalties available if the response falls short. Belgium has not completed transposition, and as of now our three regional administrations are still working through how to fold the new provisions in.
The recast introduces indoor environmental quality as a defined concept in EU building law for the first time, and Article 13(5) makes it a physical requirement. Non-residential zero-emission buildings – which every new public building has to be from 2028 and every new building from 2030 – must carry measuring and control devices that monitor and regulate indoor air quality, which in practice means a CO₂ sensor wired into the ventilation controller so the system ramps airflow up as CO₂ climbs and eases it back as a room empties, the approach engineers call demand-controlled ventilation. A sensor that sits on the wall displaying a number and doing nothing else fails the provision.
Looking for a solution that links indoor monitoring to your building’s ventilation system automatically? Check out Airscan’s Continuous Indoor Air Quality Monitoring and Smart Ventilation Solutions.
The recast also carries the Smart Readiness Indicator (SRI), an EU rating that scores how well a building’s technical systems respond to three things: the building’s own efficiency needs, the occupants’ comfort and health, and signals from the energy grid. It runs across nine domains – heating, cooling, hot water, ventilation, lighting, the dynamic envelope, electricity, EV charging, and monitoring and control – rating each on a scale from no automation to fully automated, then rolls that up into a single percentage and letter class, the same way an energy label works. The SRI stays voluntary for most member states for now, though the Commission is expected to adopt a delegated act by mid-2027, making it mandatory for large non-residential buildings above 290 kW of rated HVAC output, and it is already wired into subsidy programmes in several member states.
The recast includes two further provisions. The zero-emission building standard bars any on-site fossil fuel emissions (e.g. gas or oil boilers for heating and hot water) from new public-authority buildings from 2028 and from all new buildings from 2030 onwards. Its definition also explicitly requires indoor environmental quality to be maintained, which closes the door on hitting an energy target by starving a building of ventilation, the failure mode of early passive house construction, where an extremely airtight envelope scored beautifully on energy and then underperformed on ventilation because the mechanical system was never sized for a sealed box. Renovation passports, the second provision, are documents created for individual buildings that lays out a multi-step renovation plan to get it to zero-emission standard over time, instead of doing everything in a single renovation. They were meant to be in place by May 2026 and, like the EPBD transposition itself, are still being worked out across the EU, Belgium included. The sequencing matters because renovation steps affect each other: insulating a building changes how much heating it needs, so insulation has to happen before the heating system gets resized. Do it in the wrong order and you size the new heating system for the old, leakier (in terms of insulation) building.
Common misconceptions about EPB/PEB/EPBD
It’s important to note that each Belgian region runs its own system with its own calculation method, software tool, and interpretive guidance, so an EPB submission built in Flanders cannot be reused in Brussels or Wallonia. The parameters have to be recalculated in the receiving region’s platform. This is an easy mistake for anyone used to an EU country with a single national system.
It’s also risky undersizing ventilation in an airtight modern envelope. Good airtightness earns a higher energy score, but it also strips out any natural ventilation, which leaves the building wholly dependent on its mechanical system for every breath its occupants take. Undersize that system, commission it badly, or neglect its maintenance, and the sealed envelope holds in its own moisture and pollutants, producing condensation, mould on the cold bridges, and CO₂ that climbs through the working day. You might pass EPB but fail the other standards in indoor air quality further in this guide.
Acoustics is another potential hurdle. Moving the airflow the way the standard demands means pushing real volume, and when the ducts, grilles and diffusers get undersized to save money during construction, the air velocity required rises and the system starts to hum. In a bedroom that hum is loud enough to disturb sleep, in an office, it disturbs productivity. And the occupant’s response is to turn the system down or off, and the building then never moves the air its certificate claims.
The air at the public: the Law of 6 November 2022
Now the air has reached people, and the first of the two indoor frameworks governs the spaces the public walks into. Belgium’s federal indoor air quality law, passed in November 2022 and published in the Moniteur Belge on 1 December that year, covers any enclosed public spaces: a restaurant, a gym, a cinema, a retail shop, a hotel, a school, an event venue, a hospital waiting room, a museum, a library. This law does not cover private homes and spaces restricted to a select group of people i.e. workplaces and employees.
Originated from lessons learned during the COVID-19 pandemic, the Federal Government concluded that indoor air quality had been a decisive and unmonitored factor in viral transmission, with no legal framework governing it in public-facing spaces, and the explanatory memorandum states the aim plainly: to carry what the pandemic taught about air and respiratory disease into permanent regulation.
The new Belgian IAQ law sets two reference levels for indoor air quality, a certification and labelling system for public-facing spaces, and process obligations that are currently voluntary but expected to become mandatory in 2027 (in phases).
The two reference levels in Belgium’s IAQ law of 6 November 2022
The law focuses on measuring ventilation quality through CO₂, used as a proxy rather than a dangerous pollutant in itself. It’s a popular approach used throughout the IAQ industry: people exhale CO₂ steadily, so if we detect it building up in an enclosed space, it usually means the air isn’t being replaced fast enough, and all the harmful stuff – the viruses, mould & fungus, volatile organic compounds and other pollutants – that are already present in the room are likely building up right alongside CO2. Measuring CO₂ is a simple, practical way to tell whether a room is ventilated, and safe, for people in it.
The law sets two reference levels to grade ventilation quality in a public space:
- Level A: good air quality, holds CO₂ below 900 ppm, or delivers at least 40 m³ of ventilation and/or purified air per person per hour, of which at least 25 m³ is outdoor air. The 900 ppm figure comes from adding two things: outdoor CO₂ sits near 400 ppm and Level A allows the people and activity inside to add 500 on top. A busy restaurant reading 850 ppm is one where the air turns over often enough that most of what a diner breathes is fresh supply rather than someone else’s exhalation.
- Level B: good enough air quality, holds CO₂ below 1,200 ppm, or delivers at least 25 m³/h of outdoor air per person. It describes a room that is ventilated, so a packed lecture hall at 1,100 ppm may feel noticeably stale and anyone sensitive to air quality registers it.
These levels feed into the certification and labelling step of the broader set of compliance required of each public space.
What becomes mandatory in January 2027
These levels feed into a certification and labelling system. Once the mandatory phase begins, every operator of an enclosed public space has to install a CO2 meter, carry out a risk analysis, produce an action plan describing steps toward the reference levels, and apply for certification. The certification assigns the space a grade based on what it achieves, and that grade goes on a label displayed at entrances to give the public more information about the air quality in the spaces they frequent. A restaurant at Level A and another with no grade are making visibly different commitments to their customers.
The law has run in a voluntary phase since 1 October 2024, with compliance available but not required. On 1 January 2027 the obligations turn mandatory, and a Royal Decree will name which categories of public space have to comply first.
Once your category is designated, three obligations become mandatory:
- The first is to install a CO₂ meter in at least one per enclosed space, clearly visible and positioned away from doors and windows so it reads the air in the middle of the room rather than the fresh draught near an opening. The Royal Decree of 12 May 2024 sets the technical requirements for accuracy, calibration and display, because a cheap sensor deviating by 200 ppm turns the whole measurement into noise.
- The second is to commission or run a risk analysis, to analyse the space and activities in it, highlighting the ventilation and air purification systems in place, and identifying possible sources of indoor air pollution. The content requirements will be set by Royal Decree, but the law already defines the scope: what’s in the air, what’s putting it there, and what systems are supposed to be handling it.
- The third is to produce an action plan, required where the risk analysis flags the need for corrective action, laying out what the operator will do across 3 horizons: short term-adjustments like ventilation schedules or occupancy limits, medium-term steps like supplementary purification, and long-term capital works like installing mechanical ventilation. The plan has to aim at the reference levels.
An independent certification body is expected to be appointed and accredited by the FPS Public Health to inspect the space, verify that obligations have been met, and assign the grade to be displayed at the entrance. The certification procedure is still being developed and no certifiers have been accredited yet; and the supplementary law of 18 May 2024 confirmed a ten-year rollout of the law through to 2037, with the labelling system phased in after the obligations have taken hold.
Need an air quality risk analysis for your space? Airscan has been running indoor air quality assessments across a multitude of local, regional and global frameworks. Speak to an Airscan air quality engineer today.
The air at the workplace: the Codex on Well-being at Work
When the air reaches spaces of buildings where people are employed, that’s where Belgium’s Codex on Well-being at Work comes into play. This fourth framework is a consolidated code for occupational health and safety, containing all the implementing royal decrees of the Act of 4 August 1996 – the framework law that governs worker wellbeing in Belgium. It applies to every employer with workers in Belgium, whatever the size, sector, or country of HQ. The Codex is enforced by the Directorate General for the Control of Wellbeing at Work through administrative fines and penal sanctions under the Social Penal Code. Where the 2022 law governs the air in public spaces, the Codex governs (along with a host of other things that affect worker welfare) the air where people work: offices, warehouses, co-working space, hospitals, factory lines.
Binding numbers for air quality in workplaces
When it comes to air quality in workplaces, Book III, Title 1 of the Codex, sets the ventilation and air quality requirements for workplaces, and although the CO₂ thresholds carry the same figures as the 2022 law, 900 ppm and 1,200 ppm, their legal weight is heavier.
The purpose is the same as the 2022 law: high CO2 build up in enclosed spaces is a proxy for poor ventilation and the build up of other nasty pollutants. The employer has to take the technical or organisational measures needed to keep CO₂ in work rooms generally below 900 ppm, which corresponds to at least 40 m³ of fresh air per hour per person present. The higher threshold of 1,200 ppm, or 25 m³/h per person, is available only as a derogation, where the employer has eliminated or reduced as many indoor pollution sources as possible and created a low-emission environment. In practice, an employer who can’t get below 900 ppm has to first prove they have identified and worked every controllable source – removed or substituted emitting materials, optimised the cleaning products, conducted HVAC maintenance regularly – and only then document the justification for CO2 running higher. Reading 1,050 on the meter and reasoning that it clears 1,200 ppm – without performing the rest of the steps as outlined – does not meet the requirement.
The Codex makes one allowance for the outdoor baseline. Where outdoor CO₂ runs above the assumed 400 ppm – increasingly common in urban areas, near major roads, or at high-traffic hours – the employer may adjust the indoor threshold upward by the same margin, so a measured outdoor reading of 450ppm would permit an indoor target of 950ppm. The adjustment is not automatic: the employer has to measure and document the outdoor baseline to invoke it. The logic is mechanical: a ventilation system can only dilute indoor CO2 down to whatever the outdoor air already carries, and no lower.
How the Codex governs air quality in practice
Air quality under the Codex lives inside a Dynamic Risk Management System that every Belgian employer has to run, and the system cycles continuously through four stages – development, programming, implementation, evaluation – rather than resolving in a single assessment.
An air quality risk analysis has to be conducted to examine:
- the presence and physical activity of occupants, since ten people at desks generate far less CO2 than ten people in a CrossFit class.
- the products and materials present in the work rooms – construction materials, floor coverings, furnishings, furniture equipment.
- the maintenance, repair and cleaning of the workplace, since industrial cleaning products spike indoor pollutant levels during and after.
- And the quality of supplied air as a result of infiltration and ventilation, including the contamination, condition and operation of the ventilation, air treatment and heating system, since a clogged filter, a broken damper actuator, or a system two years without service can undermine everything upstream of it.
The risk analysis feeds two mandatory documents. The Global Prevention Plan covers a 5-year period and sets the employer’s strategic priorities across every aspect of worker wellbeing – air quality among them – while the Annual Action Plan turns those priorities into specific actions for the current year with named responsibilities and deadlines. Both require a prior opinion from the Health & Safety Committee (companies with 50 or more workers), or in its absence, from the Trade Union Delegation, or in its absence, the employees direclty. The employer must seek that opinion and cannot proceed without it, though the opinion itself is advisory.
The employer doesn’t navigate this alone. Every employer has to establish an Internal Service for Prevention and Protection at Work with at least one Prevention Advisor – a role the employer can hold personally in companies under 20 workers, and in larger companies, demands qualifications scaled to the company’s risk category. Alongside it, every employer has to affiliate with an accredited External Service for Prevention and Protection at Work, which must staff specialists across five mandatory disciplines: occupational medicine, safety, ergonomics, psychosocial aspects, and industrial hygiene and toxicology. That last discipline being the one that operationalises the air quality requirements in workplaces. When an employer needs to conduct the IAQ risk analysis, interpret CO2 readings against the Codex thresholds, assess whether ventilation systems are delivering, or build the case for the 1,200 ppm derogation, they work with their External Service’s industrial hygienist.
Where the employer runs any air-change installation – air conditioning, mechanical ventilation, any mechanical system – the Codex sets conditions on it. The system has to spread fresh air evenly across the work rooms rather than blast one corner and strand another, it has to avoid imposing temperature swings, draughts, noise or vibration that create their own discomfort, and it has to be maintained so it never turns into a pollution source itself, which is the fate of dirty ductwork, mouldy cooling coils, and humidifiers left unserviced.
How the four connect
The four frameworks govern different things, but they converge on the same ventilation system in the same building. The EPB/PEB codes determines what the system was designed to deliver. The outdoor air quality determines what it has to work with. The Codex and the 2022 law determines what the operator has to show for it – one for staff-only zones, one for public spaces, each with its own risk analysis, documentation, and enforcement path.
Where this gets practical is in buildings that carry obligations under both indoor frameworks at once. A hotel, a gym, a hospital – the employer’s Codex duties in the staff areas and the 2022 law obligations in the public areas run in parallel, through the same HVAC infrastructure, but the process for each is separate. The operator managing one building will be running two regulatory processes against the same air. For qualifying non-residential buildings, the recast EPBD will add a third, with continuous IAQ monitoring obligations that neither of the other two currently require in quite the same way.
Several of these frameworks hit deadlines within weeks of each other through late 2026 and into 2027The table below sets out what is due, when, and under which framework. Here are the dates you need to know about:
Belgium air quality compliance deadlines
| Regulation | Date | What happens |
|---|---|---|
| EU Ambient Air Quality Directive (2024/2881) | 11 December 2026 | Transposition into national law |
| EU Ambient Air Quality Directive (2024/2881) | 2026–2029 | Assessment measurements against future 2030 limits |
| EU Ambient Air Quality Directive (2024/2881) | Ahead of 2030 | Roadmaps required where measurements exceed future limits |
| EU Ambient Air Quality Directive (2024/2881) | 1 January 2030 | Binding pollutant limits take effect |
| EPBD recast (2024/1275) | 29 May 2026 | Transposition deadline (missed by all 27 member states) |
| EPBD recast (2024/1275) | 15 July 2026 | European Commission opens infringement proceedings against all 27 |
| EPBD recast (2024/1275) | 2028 | Zero-emission standard applies to new public buildings |
| EPBD recast (2024/1275) | 2030 | Zero-emission standard applies to all new buildings |
| Law of 6 November 2022 | 1 October 2024 | Voluntary compliance phase begins |
| Law of 6 November 2022 | 1 January 2027 | Mandatory phase begins; Royal Decree defines first categories |
| Law of 6 November 2022 | End of 2037 | All publicly accessible indoor spaces covered |
| Law of 6 November 2022 | 2038 at earliest | Certification and labelling becomes mandatory |
| Codex on Well-being at Work | In force now | CO₂ and ventilation obligations mandatory for every employer |
If you’re working out your obligations across these frameworks, or you need performance testing to verify your ventilation systems and test that the air indoors is safe for occupants, that’s our work.
Airscan performs air quality testing and verification against major regulatory and technical frameworks, and we also regularly deliver performance testing for global and regional certifications such as WELL, LEED, BREEAM and DGNB. We run the whole length of the airflow chain, monitoring outdoor air quality across whole cities and municipalities to the air in the rooms people occupy.
Speak to an Airscan air quality expert to discuss your project today.
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