Hygiene Standards in HVAC systems: EN 15780 and VDI 6022

Ventilation and air conditioning (HVAC) systems are the "lungs" of any building — they deliver the air we breathe at work, at home, in hospitals and production halls, in schools and kindergartens. When these systems aren't properly maintained, dust, grease, mold, and bacteria build up in the ductwork and equipment, leading to poor air quality, complaints related to "Sick Building Syndrome," and sometimes real health risks such as allergies and asthma.

That's precisely why two key documents have been developed in Europe to regulate the hygiene of ventilation systems: the European standard EN 15780 and the German guideline VDI 6022. While they pursue a similar goal — clean, healthy air — they differ in scope, origin, and application logic.

EN 15780 — the European standard for duct cleanliness

EN 15780 ("Ventilation for buildings — Ductwork — Cleanliness of ventilation systems") is an official European standard, published in 2011. It applies to both residential and non-residential buildings and covers:

• criteria for assessing the cleanliness of ductwork, filters, and air handling units (AHUs);
• methods for measuring and classifying contamination (inorganic and microbiological);
• guidelines for cleaning, maintenance procedures, and subsequent verification of results.

The core approach of EN 15780 is risk-based — for each specific system, the contamination risk is assessed depending on the building type, mode of operation, and the sensitivity of the spaces involved (for example, a hospital has far stricter requirements than an office).

VDI 6022 — hygiene guidelines from the German association of engineers

VDI 6022 was developed by the German engineering association Verein Deutscher Ingenieure (VDI) and is aimed primarily at non-residential buildings — offices, production halls, shopping centers, hospitals, and schools. Unlike EN 15780, VDI 6022 focuses more on:

• identifying potential sources of contamination (moisture, filters, humidifiers, stagnant water, room occupants, machinery and equipment);
• selecting appropriate structural and operational control measures;
• regular hygiene checks, inspections, and training of staff responsible for HVAC maintenance.

Although VDI 6022 is formally a guideline rather than a law in Germany, in practice it is treated as a de facto mandatory standard — both by equipment manufacturers and by building owners/operators — and is frequently cited in legal or insurance disputes concerning air quality.

EN 15780 vs. VDI 6022

The two documents are not mutually exclusive. Many manufacturers and operators in Europe apply EN 15780 (for ventilation system cleanliness) and VDI 6022 (for overall system hygiene) simultaneously, especially in sensitive environments such as pharmaceutical facilities, cleanrooms, hospitals, and healthcare institutions.

Conclusion

EN 15780 and VDI 6022 are not competitors but complementary tools for achieving a healthy and energy-efficient indoor climate. EN 15780 provides the European framework for assessing the cleanliness of ventilation systems, while VDI 6022 offers a more detailed, role-based set of requirements — spanning equipment design, staff qualification, and periodic hygiene inspections.

For building operators, the practical takeaway is clear: responsibility doesn't end with purchasing equipment that complies with the applicable standards — it continues throughout the system's entire lifecycle, through regular inspections, documentation, and trained personnel.

The team at "TANGRA – AV" Ltd. is the first and only certified manufacturer of TANGRA AHU air handling and ventilation units, which are tested and certified according to EN 13053, DIN 1886, VDI 6022, and DIN 1946-4. TANGRA AHU air handling units are tested and certified by both TÜV and Eurovent. This guarantees to our customers and partners that we don't just stand behind clean indoor air quality — the parameters shown on the unit's data sheet, such as energy efficiency and supply air parameters, will actually be achieved by TANGRA AHU ventilation and air conditioning systems.

VDI 6022 in detail: the parts of the guideline and who is responsible for what

VDI 6022 is not a single document but a series of related parts ("Blatt" in German, literally "sheet"), each covering a different aspect of HVAC hygiene. The TANGRA team has prepared a breakdown of the main parts and who bears responsibility for their implementation.

Part 1 (Blatt 1) — Basic hygiene requirements

This is the "backbone" of the entire standard. It defines the requirements for the design, construction, operation, and maintenance of ventilation and air conditioning systems and equipment, so that the fresh air supplied poses no health risk to occupants. It includes requirements for the materials and products used (non-corrosive, resistant to microbial growth), accessibility of components for cleaning, inspection and maintenance intervals, as well as contamination categories.

Responsibility:

• The manufacturer/supplier of HVAC equipment — must produce and deliver air handling and ventilation units and components that meet the requirements: smooth, easy-to-clean surfaces, automatic condensate drainage, materials resistant to microbial growth, and easy access for inspection and maintenance.
• The designer and installer of HVAC systems — is responsible for ensuring the system is designed and installed hygienically (e.g., correct positioning of filters, humidifiers, drains, etc.).
• The building owner and HVAC maintenance team — bears ongoing responsibility for keeping the installations compliant throughout the system's lifecycle, including organizing regular inspections and maintenance.

Part 2 (Blatt 2) — Measurement methods and hygiene checks

Part 2 supplements Part 1 by specifying the technical methods used to measure contamination and conduct hygiene checks (Hygienekontrolle) and hygiene inspections (Hygieneinspektion) — for example, microbiological surface sampling, water sample analysis (for systems with humidification), dust measurement, and more.

Responsibility:

• Qualified personnel (Category A/B, see Part 4) — carry out the actual checks and inspections using standardized methods.
• The owner or operator — commissions and pays for these checks at the specified intervals (these follow various maintenance schedules — monthly, annual, biennial, or triennial — depending on the installations and the building's purpose).

Part 3 (Blatt 3) — Hygiene standards for production facilities and industrial premises

Part 3 covers specific hygiene requirements for ventilation systems in production and industrial environments, where additional risks exist (e.g., recirculation of potentially contaminated air, specific contaminants from production processes, and others).

Responsibility:

• The owner or operator of the production facility — is responsible for adapting the general requirements of Part 1 to the specifics of the production process.
• The equipment manufacturer or installer — insofar as the system affects incoming air quality and specific indoor climate requirements.

Part 4 (Blatt 4) — Personnel qualification

This part defines the training levels required for various cleaning and hygiene activities related to HVAC systems:

• Category C — basic instruction for operators of small HVAC systems;
• Category B — for personnel carrying out servicing, inspection, and maintenance of HVAC installations (training takes approximately 1 day);
• Category A — for personnel performing more in-depth hygiene checks, design and execution of HVAC systems, and personnel taking on responsibility (training takes approximately 2 working days);
• RLQ (Certified Ventilation Hygiene Engineer) — the highest qualification level, for individuals or organizations conducting official hygiene inspections and issuing verification documents.

Responsibility:

• The operator or owner — must ensure that the personnel (in-house or contracted) servicing the system hold the appropriate qualification.
• Training organizations/certification bodies (e.g., TÜV and similar) — conduct the training itself, examine service providers, and issue certificates.

Part 5 (Blatt 5) — Requirements for humidifiers in ventilation and air conditioning systems (older versions) / related topics

Note: In different revisions of the series, the numbering and scope of individual parts change over time, as VDI periodically updates the documents. The current structure should always be verified in the official VDI catalog, since parts may be merged, renumbered, or withdrawn.

Part 6 (Blatt 6) — Air humidification via decentralized devices

Part 6 addresses hygiene requirements for the planning, installation, operation, and maintenance of standalone (decentralized) humidifiers, as well as decorative water features (fountains, water walls) that affect room humidity. This part addresses the specific risk of unfiltered, microbiologically contaminated air and inadequate maintenance of such devices.

Responsibility:

• The device manufacturer — must design the device to prevent water stagnation and microbial growth.
• The operator/owner of the premises — is required to carry out regular maintenance, cleaning, and replacement of water/filters.

Summary table of responsibilities under VDI 6022

For more information, you can contact the TANGRA – AV Ltd. team at: office@tangra.bg