Application for Air Handling Units

Air hygiene – a first step against a tremendous risk

In average a human being can sustain 30 days without food and approx. 3 days without liquid – without air breathing the dead already takes place after 3 minutes. Thus the air – with difference to everything else – is the most important „food“ for human beings. Due to the fact that a person stays within closed rooms up to 85% of the day the air handling units take care for the supply of fresh air for breathing. Accordingly this circumstance should be evaluated closer with regards to e.g the break out of influenza.

Is the air a virus carrier and due to that a way for infections with viruses? Is it possible that the air handling unit can be a carrier for viruses?

By reading the official publication of companies within the business, the general answer is „no“

By reading available scientific studies, the answer is a clear „yes“

 

The statements stating for „no“ rely on the argumentation, that hepa filters take out germs and bacteria. For offices usually hepa filters are not used. But even hepa filters do not retain any viruses due to their size.

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By considering the answer „Yes“ , an explanation within the science study of the UK RUB „Analyse der Verbreitung aerogener Viren über Raumlufttechnische Anlagen und Entwicklung von Desinfektionsmaßnahmen“ (Analysis of the spreading of aerogene viruses via air handling units and the development of disinfection methods) is given. Within this study it is proven,  that pathogen viruses are spread via air handling units. The study is explicitly stating:

„Infektionen des respiratorischen Traktes kommen häufig auch bei Personen vor, die sich in klimatisierten Gebäuden aufhalten. Diese Erkrankungen fallen unter den Sammelbegriff „Sick Building Syndrome“. Die Übertragung der Erreger kann hier auch über raumlufttechnische (RLT)-Anlagen erfolgen. Die Richtlinie VDI-6022 definiert den Stand der Technik hinsichtlich hygienischer Anforderungen an RLT-Anlagen. Die in dieser Richtlinie empfohlenen Filterstufen F5 / F7 bzw. F7 / F9 erscheinen aufgrund der Porendurchmesser für virale Erreger als uneffektiv.“

Infections are often caused by people being in ventilated buildings. …. The infections with viruses can be caused by air handling systems. The German guideline VDI-6022 is defining the current state of the art requirements related to the hygienic conditions. The recommended filters within this guideline of F5, F7 or F7 and F9 class seem to be ineffective due to the small diameter of viruses.”

Reference:

https://www.hdz-nrw.de/forschung-lehre/forschung-an-kliniken-instituten/laboratoriums-und-transfusionsmedizin/forschungsprojekte/molekularbiologische-infektionserregerdiagnostik/analyse-der-verbreitung-aerogener-viren-ueber-raumlufttechnische-anlagen-und-entwicklung-von-desinfektionsmassnahmen.html

Also within the REHVA recommendation (Federation of European Heating, Ventilation and Air Conditioning) with regards to COVID-19, an disinfection via the air is explicity not excluded but expected to be possible.

What can be done?

A disinfection for inlet and for recirculating air will minimize potential risks. A „clean disinfection“ is to be considered not to change the composition of the air or to inject external ingredients – thereof without incriminatory chemicals. For this the UV-C disinfection is superior to all other disinfection methods.

UV-C systems for air disinfection can be retrofitted within existing air handling units:
The UV-C system (with minimum pressure drop) is positioned – if possible at the outlet part of the air handling unit. Within the  module, special UV-C lamps with a wavelength of 254 nm are mounted. Only this wavelength will ensure maximum efficiency. As the modules are mounted square to the air stream, the max. efficiency is ensured.

Based on the individual requirements, disinfections rated up to 99%  can be achieved. The exact UV-C dosage which is needed for the inactivation of micro organismen is depending on the microorganism itself and can be found within the latest literature. Summing up, UV-C disinfection  can be retrofitted. Moreover UV-C disinfection can be used as a hidden reserve e.g. in the winter time to protect employees against influenza or flus

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