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. Under the term of the microorganisms, without technical aids mostly not visible bacteria and molds are summarized. An increased microbial load of the ambient air with longer exposure can lead to lung diseases, allergies and other complaints. 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 Hygiene inspections 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 (e.g. in the fire dampers). While our accredited mold laboratory determines whether your HVAC system has an increased microbial load. For this purpose, we identify, among other things, moulds 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. When taking samples in this manner, it is 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. Uneven or angled surfaces should be sampled according to VDI 6022 using sterile and moistened swabs. 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). 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.