The Delta variant of COVID-19 is spreading fast when the spring lockdown ended. We now know that this spreads most effectively through the air. What can we do to purify the air around our staff and customers, and thereby reduce the risk of infection spreading in the workplace? This month’s article reviews some of the basics, and simple tools to help keep the air clear.

The last year and a half has made us all much more aware about the risks and prevention of infection. With the end of lockdown, many people are returning to the workplace, or visiting premises previously closed. This article looks at a couple of simple measures that we can do to help safeguard our staff and our customers. First, we will start with some basic principles.

What are we dealing with?

Some bugs spread through our touching objects around us whereby we leave behind or pick up the bugs from the items touched, be they door handles, table tops, banisters, or handshakes – these are known as contagious diseases coming from contact (from the Latin verb tangere meaning to touch, and Latin noun tactus meaning a touch). These bugs only infect us when we transfer them inside us by our touching the routes into our bodies such as eyes, nose, mouth, or wounds – otherwise they just sit on our hands waiting to be transferred to other surfaces.

These compare with bugs that spread in the air, in aerosols or in dust, which we can then breathe in, and they then work their way into our system through our mouths or lungs. These we call infectious diseases (from the Latin in and factus meaning made or carried into).

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Microbiological life does get a bit more complicated, though, in that bacteria in a moist environment will be replicating themselves, and microbiological contamination on a surface will be being transferred into the air by movement and air currents.

Reducing bug counts – on surfaces

We have three principal means to reduce bug counts on surfaces.

The first is to wipe them away, and this is best carried out with soap and water, and then dried with a clean cloth – but be aware that whatever material is picked up on a cloth from one area should be dealt with correctly and not just transferred to another wider area.

The second is to apply a disinfectant, but be aware as to what the disinfectant has been designed to kill, and how much ‘contact’ time they need with a bug before the bug is killed. Some disinfectants are tested for their ability to kill bacteria, others for viruses, and others for moulds. If the disinfectants are being used to disinfect medical devices, the disinfectant is required to be CE marked as a Class IIa device as well. Be aware too that the chemicals that are toxic to the bugs may also interact with the surfaces being disinfected, and discolour them, for example.

The third is to get them into the air, and then kill them there.

Reducing bug counts – in the air

Even if we have decontaminated a surface, bugs will continue to drop out of the air back onto these surfaces, unless we can kill off the bugs that are in the air.

As a result of the pandemic, there’s been a plethora of new decontamination offerings that have been made available to us. Some are effective, while others are snake oil or smoke and mirror illusions. One cannot even go by the ‘you get what you pay for’ rule. Paying a lot more money does not necessarily make the snake oil any more effective!

Protection in smaller spaces

The technologies offered frequently include an element of filtration. There are many different types and grade of filters, and variations in the size of pores. Some filters may trap spore-laden dust, but the pores may not stop smaller items such as viruses. The smaller the pore, the more quickly the filters will get blocked, and then the system becomes ineffective. Thus these systems are probably best for handling smaller enclosed areas, or where people are meeting closely face to face (see Figure 1 for an example). These system are great for first-line defence for staff at reception desks as well.


Some technologies offer UV wavelength light with claims that the UV will kill the microbes. Only certain wavelengths of UV light (short wavelength UV-C) will be damaging to the microbes, and the effectiveness decreases exponentially with distance from the light source. Also, this UV wavelength is harmful to people, and so the equipment needs shielding, which makes it less effective.

Fogging devices are available, which put microbicidal chemicals, such as hydrogen peroxide or ozone into the air. These can be effective for deeper room disinfection, but the room cannot be used while this is ongoing, or even for some time afterwards, and the processes do not prevent reinfection.

Protection in larger spaces

Figure 2 image

There are more-sophisticated systems that create a strongly oxidising atmosphere through which the air is drawn. This kills the microbes and breaks them down completely into harmless carbon dioxide and water (for an example see Figure 2). At the same time chemicals in the air which create unpleasant smells are oxidised as well, and are thereby eliminated. These systems also drag into the air, and thus into the decontamination stream, microbes that have settled onto surfaces. These systems are ideal for reducing contamination in larger spaces, such as toilets, showrooms, open offices, etc, and thus protect staff, visitors, and clients very effectively, while allowing normal work to continue.

Where can I get help?

There’s a whole range of solutions, from the simpler to the more highly sophisticated, for many different types of situation and environment. For further ideas, why not visit a new website that’s just been launched: Or else my colleagues at can provide advice around a range of different companies’ offerings on the market, and help you work through the different options and technologies available – to find which will work for your needs, and also discuss which might not be such a good investment. There’s a number of effective solutions at only a few hundred pounds cost, but which all the same bring greater safety, protection, and peace of mind to staff and clients.

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Further items can be found at If you are interested in receiving further information on the topic, please contact

Dr Barend ter Haar has been involved in seating and mobility for over 30 years, including lecturing internationally and developing international seating standards.

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