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Inspecting the Hygiene of Ventilation and Air Conditioning Systems in Accordance with VDI 6022

Mold – Useful and Dangerous

Hygiene of Ventilation and Air Conditioning Systems

These days, when the summer is always getting longer and hotter, and temperature records seem to be breaking daily, more and more companies and private households are installing heating, ventilation, and air conditioning systems (HVAC for short) in order to cool their offices and living spaces. At least in the context of companies in Germany, the Occupational Health and Safety Act (2019 § 4, par. 3) and the Workplaces Ordinance (2016 § 4, par. 3) regulate the hygienic and technical standards for operating HVAC systems and obligate the operator to have hygiene inspections (every 2-3 years; depending on the system) conducted by a competent and independent third party.

VDI 6022 Blatt1

The specific guidelines for the hygienic standards for HVAC systems have been described in VDI 6022 Sheet 1 since the year 1998. In summary, this document states that an HVAC system must not emit air that is of poorer quality than the air that is pulled into the system (exterior air or also interior air in the case of air circulation systems). This deterioration in air quality not only concerns inorganic particles (e.g. asbestos or mineral wool in older systems), but, first and foremost, contamination due to organic particles in the air, i.e. airborne microorganisms. These microorganisms include more than just the well-known bacteria such as Legionella sp. or Pseudomonas aeruginosa, but also quite often a wide range of mold species. With longer exposure, even low concentrations of microorganisms in the ambient air can lead to lung diseases, allergies, and other adverse health effects. Microorganisms therefore pose a hygiene threat that should be taken seriously. The GBA Group has therefore developed into a competent, independent, and reliable service provider for all of your questions regarding the technical and hygienic demands for HVAC systems. With our accredited asbestos analysis, for example, we determine whether your system represents a potential source of asbestos and mineral wool fibers. With our second focal point, microbiological analysis, we test your system for hygienic deficiencies and identify microorganisms from the relevant risk groups (e.g. in accordance with TRBA 460:2016).

Hygiene inspections

With a routine hygiene inspection, in most cases samples are taken through surface contact. Two different culture media, one for mold (DG18-medium) and another for bacteria and yeast (TSA-medium), are pressed onto a surface in order to detect the microorganisms present there. After a defined incubation time of two days for TSA or seven days for DG18, the colony-forming units (CFUs) are counted and in certain cases identified. When taking samples in this manner, it is especially important to test representative parts of the HVAC system. This includes, for example, a reference sample before the filters and components afterwards, such as the damper register, cooling battery, condensate tray, humidifier, ventilation chamber, droplet separator, air supply duct, air outlet, etc. For components with an uneven surface, it is advisable to sample them using sterile swaps. The GBA Group has developed their own method for this and enhanced it in order to improve the detection limit as well as the retrieval rate for microorganisms in swab samples. The most recent revision to VDI6022, published in 2018, requires not only surface contact and swab samples, but also direct testing of the indoor air. For this form of testing, the microorganisms in the air are isolated with the help of microbe collectors on culture media (DG18 and MEA and/or DG18 and TSA). However, ambient air poses a great challenge for many laboratories. As opposed to contact or swab samples, it’s not enough just to count the CFUs for each surface. According to VDI6022:2018 Sheet 1, the molds that are present must be identified by an accredited laboratory, down to the genus and species if possible. In our accredited mold laboratory, we conduct precisely this kind of identification and demonstrate our ability to detect common indoor mold species regularly by participating in interlaboratory proficiency tests and other external audits.

Microbiological Laboratory Services:

Regarding aspects of category A air hygiene training in accordance with VDI 6022

In addition to our accredited laboratory for mold and asbestos analysis, we also have an experienced team that can provide you with competent support regarding aspects of category A air hygiene training in accordance with VDI 6022 Sheet 4. We will gladly consult you on the planning and execution of hygiene inspections. When all of the preparations have been completed, you will receive all of the necessary materials, sampling pumps (microbe collectors), and certified culture media for your project. After the sample-taking process is completed, you simply send it all back to use and then, after the required incubation time of seven days (DIN ISO 16000-17:2010), you receive a comprehensive laboratory report on the hygienic state of your HVAC system as soon as possible. Upon request, we will also gladly organize uninterrupted refrigerated transport conditions for your samples, as required by DIN EN ISO 18593:2018-10. It’s also no problem for us to analyze humidifier water, recirculating waters or even thermophilic molds.

Do you still have any questions on the topic of hygiene inspections of HVAC systems, or any specific upcoming projects? Then get in touch with us at any time. Our team is looking forward to hearing from you!


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