Inside job


We need a more technology-based approach to keeping people safe and comfortable inside buildings, especially as we move into the colder autumn and winter months, according to Tim Mitchell, Sales Director of Klima-Therm

Pandemics are by no means new; they have played a major part in shaping human history throughout the ages. Indeed, history shows us that, although upsetting and sometimes painful, what we are experiencing now with COVID-19 is far from unique.

The Black Death, for example, which spread in the 14th Century is estimated to have killed more than 25 million people in Europe alone – almost a third of the continent’s population. An estimated 500 million people around the world fell victim to Spanish Flu between 1918 and 1920.

The Asian flu in 1957-1958, meanwhile, killed close to 1.1 million people and around the same number are thought to have died as a result of the Hong Kong flu pandemic of 1968-1970.

More recently, we have witnessed lethal outbreaks of Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS), not to mention the shockwaves caused by the AIDS epidemic.

However, quite apart from the pain and misery caused by the latest pandemic, COVID-19 has also brutalised economies, triggering a near-total shut down of social and economic activity around the globe.

This has led to a scramble to find ways to mitigate the effects of COVID-19. There are, essentially, two broad measures you can take to protect yourself and others from this infection as well as other pathogens – practising good hygiene and mechanical safeguards.

Sensible precautions

Practising good hygiene includes frequent hand washing; avoiding touching your eyes, nose and mouth; socially distancing; cleaning and disinfecting frequently touched objects and surfaces and coughing or sneezing into your bent elbow rather than into your hands.

However, while these precautions are eminently sensible, they are fairly general in nature and the building services sector is unable to influence them. Mechanical safeguards, on the other hand, are an entirely different matter.

Recent research has proved that airborne transmission of pathogens, including COVID-19, is a clear and present danger to building occupants. Microscopic respiratory droplets generated by talking and breathing can remain suspended in the air for minutes or hours and move many metres horizontally before infecting people, according to highly respected professional sources.

More than 200 experts from 32 countries, for example, have published a commentary in Clinical Infectious Diseases, a peer-reviewed medical publication, that appeals to medical professionals to recognise the potential for airborne spread of COVID-19.

The authors include physicians, epidemiologists, and experts in environmental health and building design. They warn: “Studies… have demonstrated beyond any reasonable doubt” that airborne droplets can pose a risk beyond 2m from an infected person.

HVAC can reduce exposures

Meanwhile, in the US, ASHRAE has confirmed that transmission of COVID-19 through the air is sufficiently likely that airborne exposure to the virus should be controlled. It says: “Changes to building operations, including the operation of heating, ventilating, and air-conditioning [HVAC] systems, can reduce airborne exposures.”

Improvements to indoor ventilation, as well as the use of airborne infection controls such as filters, ultraviolet (UV) lighting and air purifying ionization technology can help to alleviate the problems associated with the airborne transmission of bacteria and viruses.

High-efficiency particulate air (HEPA) filters comprise a mat of fibres, typically glass fibre, with diameters between 0.5 and 2.0 micrometres (μm). These filters can stop viruses and bacteria (the typical length of a bacterium is 1–10 μm). However, they have a higher resistance to air passing through them than regular air filters so upgrading a ventilation system to HEPA filters could prove problematic without redesigning the entire system.

Danger to people  

Using UV light to kill micro-organisms – so-called ‘germicidal irradiation’ – also has its 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 earlier this year that only one type of UV can reliably deactivate Covid-19 – and it’s extremely dangerous.

“You would literally be frying people,” he said (

UV-C (short wave UV light) can certainly kill micro-organisms] However, as Mr Arnold pointed out, “UV-C is really nasty stuff – you shouldn't be exposed to it.”

He added: “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.”

Of course, if UV lights are specified, they will normally be housed within the AHU plant and therefore not be 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 in into the room but will not affect contaminated air already present, or created in, the room.

Natural bio-light climate

A more practical method of purifying the air – and one that can easily be retrofitted to a typical HVAC system – is via bipolar ionization. Much like sunlight in the atmosphere, this 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 neutralizing particulate matter, bacteria and virus cells, odorous gases and aerosols, and volatile organic compounds.

In practice, airborne particles 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 neutralized.

Oxygen ions cause a chemical reaction with volatile organic compounds (compounds that easily become vapours or gases), breaking down their molecular structure.

Bipolar ionization technology is superior to reactive air purification methods such as ‘end-of-pipe’ solutions that use a ‘pass-through’ or ‘filtered’ approach because it proactively treats the air in the occupied space at the source of contamination.

Tests conducted by the Spanish government show a reduction in a coronavirus surrogate by 99% airborne and 80% on surfaces in 10 minutes by using plasma air ionizers.

Laboratory analysis

The research tests were conducted in a Madrid hotel converted into a residence and confinement centre for medical staff during the pandemic. The experiments took place in simulated ICU hospital rooms within the hotel. This environment was explicitly designed to test air ionization on small aerosolized viral particles. The laboratory analysis was carried out at a nearby operations centre of the Spanish Ministry of Defense. 

For the best protection against COVID-19, good hygiene practice must continue even after installing any of the three systems mentioned here, but I would argue that, when it comes to tackling airborne infection, bipolar ionization is a first-class option.

Bipolar ionization in action

Sketch, a three Michelin-star rated restaurant in London’s Mayfair founded and owned by Mourad Mazouz, has recently retrofitted a bipolar ionization air purification system to its existing ac system and is the first UK application for this technology available from Klima-Therm.

Mazouz’s number one priority is the wellbeing of those in his care. As he points out: “Restaurateurs have a duty to look at all possible solutions to fight against the spread of coronavirus in order to protect their customers and employees.”

This commitment to protecting the people under its roof led Sketch to become the first restaurant to be retrofitted with the innovative air purifying system. Bipolar ionising air units purify the restaurant’s airflow, decreasing the number of viruses and bacteria suspended in the air by an impressive 95%.

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