Clean air has never been more important, whether delivered via ventilation or air purification. But with so many products on the market, how do you choose the right one for your needs?
As the world emerges from lockdown and people start to gather again in indoor spaces, the threat of airborne transmission escalates.There is evidence to suggest that, after a protracted period of social distancing and mask wearing, people have weaker immune systems to defend themselves against the onslaught of respiratory viruses like flu and the common cold, as well as Covid-19 and its variants.
Businesses are rightly concerned about protecting their employees, customers and other stakeholders. As a by-product of that protection, they also want to reduce absenteeism and increase productivity, two further advantages of good indoor air quality.
In the USA, poor air quality results in $150 billion of illness-related costs per year. Of that, $93 billion represents lost productivity from headaches, fatigue, and irritation associated with sick building syndrome (Source: National Oceanic and Atmospheric Administration).
A study quoted by the World Green Building Council suggested that enhancing indoor air quality could be as effective in reducing aerosol transmission of viruses as vaccinating 50-60% of the population*.
However, many buildings struggle to achieve the World Health Organization’s recommended air change rate of 10 litres per second per person. That’s where air purification comes in, either working in isolation (single or multiple units) or to supplement an in-built Heating, Ventilation and Air Conditioning (HVAC) system.
It’s critical to choose the right technology for the job. In its June 2021 update, the Centers for Disease Control and Prevention (CDC) recommends High Efficiency Particulate Air (HEPA) filtration systems to capture COVID-19 particles, with germicidal ultraviolet light (UVC) as a supplemental treatment to inactivate the virus.
Why HEPA? Because it traps 99.97% of particles whose diameter is equal to 0.3 microns, with the filtration efficiency increasing for particle diameters both less than and greater than 0.3 microns. Covid-19 particles are typically 0.1 microns in size as aerosols and above 10 microns when enveloped in respiratory fluid, meaning that HEPA captures 99.99%. HEPA is even proven by NASA.
The CDC also stipulates a powered fan system. This is important as an air purifier that does not circulate air is effectively useless. Residential air purifiers using HEPA will not serve as a substitute for a hospital grade device containing a powerful fan.
The fan creates high static air pressure, which is necessary to allow sufficient air to flow through the HEPA filter and to boost air cleaning performance throughout an entire space, rather than just the air around the machine itself.
The best medical grade air purifiers succeed in balancing high air circulation with relatively low noise levels. The lowest setting is typically 45dBA, an even white noise equivalent to the recommended white noise level limit for an infant sleep machine.
Harmful side effects are associated with the kind of air purifiers sometimes referred to as using ‘additive’ technologies (based on indirect chemical reaction) as opposed to ‘subtractive’ (filtration and direct inactivation).
In her Open Letter to address the use of Electronic Air Cleaning Equipment in Buildings, Dr. Marwa Zaatari – eminent US Indoor Air Quality expert and Member of the Board Of Directors at U.S. Green Building Council – quotes the UK’s Scientific Advisory Group for Emergencies, which warns that “technologies based on UVA/UVB, ionisation, plasma, electrostatic precipitation and oxidation methods have limited evidence of efficacy against the virus and/or significant concerns over toxicological risks during application”.
The main substance to avoid is ozone, which can cause irritation of and damage to the small airways of the lung.
UVC light inactivates bacteria and viruses by breaking down their DNA and RNA, thereby effectively destroying them. It is recommended by the CDC but there are two important issues to bear in mind: the first is that the ultraviolet lamp must be enclosed (so as not to harm the eyes) and the second is that the wavelength must be above 240 nanometers (to ensure that no ozone is produced).
Reputation can be misleading, as many big global brands have added air purifiers to their product ranges. However, such household names generally make small devices for residential use only, not hospital grade units fit for purpose in an office or commercial environment.
Marketing claims can be exaggerated and unsubstantiated, making it a challenge for most engineers and consultants to discern fact from fiction, let alone the managers of companies, schools, care homes, surgeries, shops and hospitality venues.
The key is to look for:
Manufacturers’ own tests are not enough.
Furthermore, look for case studies in your sector and contact a couple of quoted customers to obtain a first hand account of their experience. Most people are happy to share their views if it helps others to make an informed decision that can help protect public health.
Check out the manufacturer’s sustainability credentials, especially the potential to recycle both the product itself and the consumables.
The final tip is to think of the purchase as an investment rather than simply a cost. When it comes to the capital cost, compare like with like. A small residential air purifier will always be far cheaper than a hospital grade unit and, not surprisingly, far less effective. You get what you pay for.
Also, compare the cost of a batch of portable air purifiers against that of installing a new integrated HVAC system. Not only will it tend to be a fraction of the outlay, it’s a solution that can be put to work immediately, with no adverse impact on business continuity. Modern HVAC systems can certainly be the ideal solution, but for many buildings the cost and disruption during installation are prohibitive.
Looking ahead, it’s worth remembering that you own the air purifiers you acquire and, if you move premises, they come with you. HVAC systems belong to the building.
The last point on cost is arguably the most important: low ongoing charges. Air purification units consume very little energy and – like a fridge freezer – cost just a few cents a day to run. This is minimal compared to an in-built HVAC system. Further substantial savings can be made on energy (and associated carbon emissions) from not having to heat or cool fresh air intake. The ongoing savings can quickly offset the initial capital cost of the air purifiers.
Given the importance of protecting health, due diligence is advisable when selecting air purifiers. The CDC encourages buyers to exercise caution and do their homework.
The key pointers when specifying air purifiers are to opt for proven technology that is endorsed by national and international health authorities. Then back up that technology with robust air circulation and evidence of independent tests.
For a relatively small investment, and low ongoing costs, your business can achieve a high standard of indoor air quality. Choose wisely and the right air purifier can serve as a 24×7 bodyguard to protect and enhance the lives of employees, customers, patients, students and visitors alike.
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