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Building an air force

Ensuring ventilation is effective by providing regular air changes is key to reducing the airborne spread of viruses such as COVID-19. Roberto Mallozzi, managing director of Klima-Therm, explains the role of filters and HVAC disinfection systems in the battle against coronavirus and other pathogens

A host of potential COVID-19 vaccines are currently in development, with several large clinical trials now reporting results. However, even if a vaccine is shown to be safe and effective, it must then be approved by national regulators before being manufactured and distributed.

In the meantime, we – as members of the building services sector – have a special responsibility to help mitigate the spread of the virus.

Most transmission occurs indoors, much of it from the inhalation of airborne particles that contain the coronavirus. The safest indoor space is one that is well ventilated.

As well as effective ventilation, however, there are also several technologies that can help lessen the risk of airborne COVID-19 infection. Three are of particular interest in the context of COVID-19 – filter air cleaners, ultraviolet (UV) light and ionizing technology.

Filter air cleaners (also known as air purifiers) remove particles from the air, usually using a filter made of tightly woven fibres that can seize particles containing bacteria and viruses to help reduce disease transmission. The best option is a cleaner that uses high efficiency particulate air (HEPA) filters as these remove more than 99.97% of all particle sizes.

Alternatively, technology is available that uses UV light to kill or deactivate micro-organisms by disrupting their DNA, leaving them unable to perform vital cellular functions. This disinfection method – sometimes referred to as ‘germicidal irradiation’ – is claimed to decontaminate surfaces within seconds.

However, it has problems. Dan Arnold, who works for UV Light Technology, a company that provides disinfecting equipment to hospitals, pharmaceutical companies and food manufacturers, told the BBC recently that only one type of UV (UV-C very shortwave UV light) – can reliably deactivate COVID-19, but it’s extremely dangerous ( 

Mr Arnold warned: “It can take hours to get sunburn from UV-B, but with UV-C it takes seconds. If your eyes are exposed… you know that gritty feeling you get if you look at the sun? It’s like that times 10, just after a few seconds.”

If UV lights are specified, they are normally housed within the air conditioning plant and are therefore not visible. That means they would only pose a risk to maintenance operatives who didn’t switch the lights off before opening the doors of the AHU. Nonetheless, the point remains that UV-C is particularly dangerous to people.

Both filters and UV will clean the air coming into the room, but will not affect contaminated air already present, or created in, the room.

For this, bipolar ionization technology can be used. This is superior to reactive air purification methods because it proactively treats the air in the occupied space at the source of contamination. Bipolar ionizing air units are also:

• Safe.

• Fast and easy to install, avoiding costly and time-consuming disruption.

• Inexpensive.

• Exceptionally energy efficient.

• Highly effective at removing the COVID-19 virus as well as other pathogens and larger particulates.

• Easily adapted to fit existing HVAC equipment.

• Low-maintenance and therefore economical to operate in the long-term.

So how do they work? 

Like sunlight does in the atmosphere, bipolar ionization produces a natural bio-climate rich in positive and negative oxygen ions. 

The negative ions contain an extra electron while the positive ions are missing an electron, resulting in an unstable condition. In an effort to restabilize, these ‘bipolar ions’ seek out atoms and molecules in the air to trade electrons with, effectively neutralising particulate matter, bacteria and virus cells, odorous gases and aerosols, and volatile organic compounds.

In practice, airborne particles – including viruses such as COVID-19 – are charged by the ions, causing them to cluster and be caught in filters. As they divide to reproduce, bacteria and virus cells bond with oxygen ions and are destroyed. Odorous gases and aerosols oxidize on contact with oxygen ions and are neutralised.

Klima-Therm can supply an ionizing air purification solution that is tailormade for each client, taking into account its specific requirements and circumstances. It can also offer valuable advice on the complete HVAC system and how to maximise its efficiency and cost-effectiveness. 


Sketch comprises restaurants, bars, a contemporary art gallery, and including the Lecture Room & Library, a three Michelin-star rated restaurant, on Conduit Street in London’s Mayfair.

Founded and owned by restaurateur and entrepreneur Mourad Mazouz, Sketch is the first restaurant to be retrofitted with an innovative air purifying system available from Klima-Therm. 

Ground-breaking bipolar ionising air units purify the restaurant’s airflow, decreasing the viruses and bacteria suspended in the air by a whopping 95%.

Asked, what business benefits she expected to see from this installation, a Sketch spokesperson said: “We expect this to protect the overall health of our guests and staff and to demonstrate that Sketch takes health and safety extremely seriously, particularly considering the changing landscape of the world around us and how health and cleanliness is so vital, now more than ever.”

16 December 2020


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