By Eamonn Ryan

Most people are aware that outdoor air pollution can impact their health, but indoor air pollution can have an even more harmful health effect given people spend approximately 90% of their time indoors.Air treatment has become essential in building spaces for many reasons – including the management of airborne pathogens which potential tenants prioritise amid growing concern around steadily worsening pollution. Many existing buildings have little option but to retrofit by having specialist services performed on their HVAC equipment. For new builds, technology can be included from the design stage.

There are many risks attached to air and air treatment of buildings, but technology exists for the HVAC engineer and contractors to include. These range from physical treatment such as ozone, nano silver, UV, as well as products available for sterilisation where required.

At its basic level, airborne contaminants can be split into natural and man-made. Pathogens like viruses (of which Covid-19 is today the most infamous, but there are many) and bacteria fall into the first category, as well as pollen and mold. Man-made contaminants come in the form of gases, chemical vapours and pollution particles.

The differing techniques of air purification enjoy varying degrees of effectiveness. For instance, filters with a minimum efficiency reporting value (MERV) of eight can capture pollen. MERV 11 filters capture mold spores and pollution particles, while MERV 13 filters can capture viruses, as well as bacteria and indoor tobacco smoke.

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Ventilation systems have a range of techniques able to help reduce air pollutants and microorganisms. These include:

  • Filtration
  • Ventilation
  • Humidity control
  • UV lighting
  • Ionisation

Let’s take a look at each of these:

Filtration: Air filters are rated for efficiency at removing particles of different sizes, and MERV ratings of 13 or 14 are recommended by ASHRAE for HVAC systems in buildings. The most penetrating particle size is 0.3 microns – in comparison a virus such as SARS-CoV-2 particles have diameters between 0.06 and 0.14 microns. MERV 13 filters are more than 75% effective at trapping coronaviruses and similar-sized viruses. HEPA filters can trap over 99% of 0.3-micron particles, but put strain on an HVAC system creating other problems like stagnant air or differences in room pressures. Consequently, they are usually only used in hospital environments and other healthcare settings.

Airflow and ventilation: Good airflow does much to reduce contaminants. The CDC (Centre for Disease Control and Prevention, the US national public health agency) recommends buildings open outdoor dampers as high as 100% to allow the maximum amount of fresh air, though this can be hard to achieve if it’s extremely hot or cold outside. Maximising ventilation is important, but there’s a balance between that goal and energy efficiency. Taking in 100% fresh air without recirculation requires more energy from the HVAC system since it needs to condition all of it. A solution is to use an energy recovery ventilator (ERV) which rotates between intake and exhaust air streams. A wheel transfers the temperature and relative humidity of the conditioned exhaust air stream to the intake air, and vice versa.

Humidity: Lower humidity allows viruses to survive longer and reduces some of the body’s natural respiratory defences. A typical example is climate control during long range flights, where air is cooled down to extreme levels without being humidified, hence quite a few people present with some kind of respiratory or breathing problems. Post-Covid, ASHRAE recommends building environments be kept between 40% and 60% humidity. Above that range, other issues like bacteria, fungi, and mites can develop.

UV-C lights: These can be used in ductwork to neutralise pathogens in moving air and wet surfaces like evaporator coils. There are different applications:

  • In-duct UV to disinfect air
  • In-duct UV to disinfect surfaces
  • Upper room UV

Ionisation: Bipolar ionisation creates ions out of oxygen which attach themselves to microparticles, bacteria, and viruses, which has been used in the healthcare setting for many years and been effective at reducing viruses such as Covid-19 and SARS in the past. The ions are over 99% effective at deactivating a virus’ ability to infect a victim, as the technology has improved in recent years, reducing the cost of installing a unit.

Ozone: Ozone is a reactive gas that kills bacteria and viruses, which can be used for disinfection of unoccupied spaces if it’s handled properly by a professional cleaning company. But it’s generally ineffective for continuous use in HVAC systems.

Clive Donnelly, mechanical engineer at BD&O Group, lists the two most popular types of air purifiers as bipolar Ionisation; and UV-C radiation. “Both have been around for a long time. UV-C works well but has its drawbacks and can be dangerous. Bipolar ionisation has proven successful over the last 25 years and was tested to great affect with SARS CoV-2 virus simulations. It has also been successfully used in the food industry to reduce bacteria from a space.

“Filters and UV-C only treat the air that passes through them, so they are dependent on good airflow, while bipolar ionisation treats the air which then goes into the space to improve the indoor air quality (IAQ). Consequently, based on the draw backs of UV-C, we recommend bipolar ionisation to our clients.”

Shift to clean air tech can reduce energy costs by up to 25%

As commercial property owners and managers look for every available competitive edge to attract and retain good tenants, great IAQ has become more than just a compelling sales point. UVC GI disinfection systems are not only delivering cleaner, healthier air, but can reduce energy costs by up to 25%.

“South African commercial property is struggling to regain Covid losses as owners and managers face a ‘Catch-22’. With weak property demand and oversupply, finding compelling differentiation such as a healthier work environment, must be weighed up against the investment required to install or upgrade IAQ systems. When that investment produces a rapid ROI the decision to move to UVC GI becomes a simple one,” says Edward Hector, MD of the SFI Group.

The UV-C wavelength has more than twice the energy of other UVs and is easily absorbed by organic substances, rapidly destroying molecular bonds. This means UVC GI can be used to safely eliminate and prevent the build-up of organic material on coils, drain pans, and interior air-handling surfaces. It improves airflow and can maintain and even return heat-transfer levels to ‘as-built’ capacity, delivering solid improvements on HVAC system efficiencies.

Clean systems reduce odours, as well as allergens or pathogens in airstreams. They help sustain design temperatures and airflow, ensuring buildings meet all required IAQ codes and standards.

“This cleaner environment means less energy is needed to provide the necessary amount of cooling and airflow to maintain system energy efficiency. We have found that UV-C installed even in older systems reduces energy use by 10-25% on average, reducing carbon footprints,” says Hector.

“When it comes to UVC GI’s benefits, one way of measuring the effectiveness of UVC GI is based on various case studies using what is called the U-value. We use U-values to measure a cooling coil’s thermal performance. The higher the value, the more efficient the operation. In a recent case study of an office block, we saw annual chilled water volume reduced from 28 849 to 18 507 tonnes – a reduction of 35.8%. Our client saw an annual saving of R10 000 for a single coil,” Hector says.

“Offering companies the highest grade of protection from highly transmissible influenzas, tuberculosis and other airborne diseases is a winning sales point in an environment where employers are trying to coax workers back to the office. Employers have enormous choice in premises right now and so decisions can turn on features like air quality and other health benefits. Disinfectant technologies, like UVC GI, deliver selling points as well as cost savings, making the immediate return on investment compelling,” Hector advises.

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Treating circulated room air and supplying fresh air

Rickard Air Diffusion specialises in air distribution and has developed a product, the Rickard UV Air Purifier, that treats air with UV light, purifying it of pathogens.

Healthcare organisations and hospital administrators are using UV light to disinfect hospitals with wall mounted units or mobile UV-C units. Mark Rickard, director of marketing at Rickard Air Diffusion, says: “It combines the protective power of UV-C light and the performance of diffusion to give a diffuser that not only keeps tenants comfortable but reduces the risk of exposure to viruses. Rickards’ patented UV induction treatment system induces air from the room and through the diffusers’ UV treatment zone where it is treated. The induction system is quietly powered by the discharge of conditioned air and therefore does not need fans or external power.

“This treatment strategy is particularly effective as it treats circulated room air and supplies fresh air. In this way, pathogens within the room are treated by UV light and the viral load is reduced by adding fresh air. VAV diffusers are also excellent at providing air circulation without creating drafts. Since the velocity drops to below 0.25m/s in the occupied zone, pathogens are less likely to be spread if a contaminant is present,” says Rickard.

“If a floor’s return air is mixed with fresh supply air as is the norm, we recommend the return air be treated with UV light in the duct. This will ensure that uncontaminated air is supplied. The UV Air Purifier is able to deactivate approximately 95% of viruses in the Corona category in a typical room (4.5 x 4.5m x 2.4m) in less than an hour. The performance depends on the diffuser size, neck pressure and room size. The combination of air purification, clean air supply and low draft rates makes the UV Air Purifier the answer to the threat of viruses in a space,” he says.

Portable standalone units use an enclosed UV-C light and a fan to suck air over the light. In this way air contaminated with viruses and fungi is deactivated. Rickard’s UV Air Purifier is integrated with the diffuser allowing for a clean open space for the occupant

“We’ve sized everything according to the volume of air that is induced through our diffuser, when it is supplied with air at normal pressures. It can treat the air of a typical room in 30 to 60 minutes under these conditions.

“By supplying fresh air through our diffusers we provide a dilution effect of the virus as well. We designed this for Covid, and it has similar application for sick buildings, hospitals, and a normal office environment. There is a faceplate over the diffuser to induce the air over the UV light and ensure that the UV levels are below 0.2 microwatts per centimetre squared at the occupant level. We have a certified laboratory meter to test and ensure it’s safe,” says Rickard.

The system can function either to retrofit a building or as part of a new design, he says.

Technologies available to engineers to include in the original design of a building

Most buildings recirculate the air through the building to some degree, with about 30% fresh air being the minimum requirement and 70% recirculated. Rickard advises removing particulates using HEPA filters, though UV-C lamps can also be put in the ducting sized according to the volume air and velocity through the ducting.

“There are some new products coming out in the UV-C space, such as large ceiling fans for industrial applications and other big-volume areas, with the blades fitted with UV-C lights in the back. There are also diffusers that treat supply air with plenum boxes and a UV-C light fitted inside each. However, it’s actually easier and more cost effective to fit a UV-C light near the centralised air unit upstream to treat supply air,” says Rickard. “We believe our unit is unique as it treats the air in the room rather than just the supply air.

“When it comes to the installation of UV-C lights or HEPA filters to purify the air in a duct the designer needs to understand where the air is coming from to ensure that they’re treating air that won’t be contaminated with return air after it is supplied. In an office environment you want to install products that treat the room air in high circulation areas like boardrooms and mixed office spaces first and then rooms with lower occupancies.

“Our UV Air Purifier doesn’t use much energy and it wouldn’t make much impact on your electricity bill, but the lamps need to be replaced annually, and the units have a finite life span. To stay effective, the lamps need to be cleaned when dust builds up.” Most bulb manufacturers such as Philips, GE and Sylvania state that their UV C lamps have a life cycle of 9 000 hours and need to be changed every 12 months.

“The installation of UV-C lamps in units has been found to damage filters, filter frames and non-metallic components. Depending on the cleanliness of the building, filters need to be periodically cleaned and replaced based on the pressure differential across the filter and the pressure drop across them – or they may use a lot of energy or just poorly circulate the building,” says Rickard.

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Do I need air purification?

Clive Donnelly of BD&O Group says: “The simple answer is that every enclosed occupied space should have air purification. It augments traditional ventilation and air cleaning systems that come standard in offices, shopping centres and hospitals.

“As most people spend about 90% of their time indoors, IAQ matters to all of us for the reason that providing a good indoor environment is the main reason why we erect buildings. A bad indoor climate can have a negative impact on issues such as your family’s health, work productivity, study performance and human comfort. Loss of work performance caused by poor air quality due to increased pollution load/ decreased ventilation is experimentally estimated to be 5%, while the cost of providing a good indoor air quality in office buildings is less than 1% of the labour cost.

“Recovering that lost 5% work performance equates to an additional 25 minutes per person per day; reduced number of breaks in work; 10 fewer sick leave days per person per year – suggesting that an investment in air quality is highly profitable,” suggests Donnelly.

This is because labour cost is:

  • 25 to 100 times higher than energy cost
  • 25 to 100 times higher than maintenance cost
  • Roughly 4 to 15 times higher than renting cost
  • Roughly 4 to 40 times higher than construction costs

Air quality and Covid

Donnelly explains that the Covid-19 pandemic highlighted how infections with respiratory viruses are principally transmitted through three modes:

  • Contact transmission is infection spread through direct contact with an infectious person
  • Droplet transmission is infection spread through exposure to virus-containing respiratory droplets
  • Airborne transmission is infection spread through exposure to those virus-containing respiratory droplets comprised of smaller droplets and particles that can remain suspended in the air.

He lists the health benefits when air purification improves indoor air quality and occupant well-being:

  • It kills or deactivates more than 99% of airborne viruses
  • There is a more than 95% reduction in microorganisms such as bacteria and spores of molds
  • A reduction in TVOCs (total volatile organic compounds)
  • Less headaches, fatigue, infections, asthma and breathing disorders
  • Less absenteeism and greater productivity
  • Air purification systems come in different modes and sizes and can be installed in central HVAC systems to serve a building or provided to single spaces.

“The SARS CoV-2 virus that carries Covid-19 is not going away anytime soon, as experts expect to be trying to contain mutations for the next ten years. UV-C radiation is a known disinfectant for air, water and non-porous surfaces, while UV light is known to kill superbugs like MRSA, VRE, K pneumonia and C difficile and are helping hospitals to reduce the transmission of superbugs that linger in hospital rooms causing new infections. UV-C has proven successful in reducing the spread of bacteria such as tuberculosis.

“UV-C has shown it can destroy the outer protein coating of the SARS coronavirus, leading to the deactivation of the virus. UV-C can only inactivate a virus if the virus is directly exposed to the radiation. If the virus is covered by dust or other contaminants such as bodily fluids UV-C is not as effective.

“There are different quality UV-C lamps on the market with the lower quality lamps requiring a longer exposure time to provide effective inactivation of the microbiological bacteria or virus. For safety reasons UV-C lamps must be installed in an enclosure such as a duct or air handling unit. Direct exposure to UV-C lamps can cause damage to the human skin within seconds and can damage your eyes.”

Donnelley adds that UV-C lamps by themselves do not save energy. He explains: “UV-C lamps can be installed to clean coils, filters and drain pans of any build-up of microbial bacteria. This in turn minimises the pressure drop across a coil and therefore reduces fan power which saves energy.”

Bi-polar ionisation.

Navigating the Covid-19 pandemic and its aftermath is one of the biggest business challenges of our time. The health and safety of the workforce is management’s top priority, safeguarding their well-being being paramount because no plan to resume normal operations can succeed without them, he notes.

“Businesses now have the chance to improve the indoor air quality of their premises thanks to a technology that removes airborne virus particles from the air, supporting the safe reopening of offices and businesses for staff and customers. Ionair emulates nature’s natural cleaning process by enriching the indoor air with oxygen ions which clean the air naturally,” says Donnelley.

“The air near a waterfall is perceived as invigorating and fresh. The reason for this is its extremely high ion content. This indicates that natural fresh air has a high ion concentration. A natural ratio of ions in the air supports absorption of oxygen by human beings and makes a significant contribution to healthy indoor air. Ionisation occurs naturally in the environment, found in places such as rays from the sun, thunder or lightning strikes or wherever water collides with itself like a waterfall or on the ocean shore.

Ionair was recently tested in the Fraunhofer Institute of Building Physics in Germany which concluded that ionair reduced the concentration of viruses by 99.5%.

Disinfectant spray based on nano silver technology

Dusan Stefanov, mechanical engineer at ODA Design & Drafting explains that nanotechnology is an advanced field dealing with the manufacturing of different nano-materials which have biomedical application.

‘Nano’ – one billionth of meter: nanoscale materials have achieved considerable attention as novel antimicrobial agents due to their high surface area-to-volume ratio and distinct physical and chemical properties.

“Silver is a natural antibiotic and has been used as an antimicrobial agent for centuries. It is effective against a broad range of pathogens such as bacteria strains, yeast, fungi, germs, viruses and protozoa. All pathogens are single cell anaerobic organisms. An anaerobic organism or anaerobe is any organism that does not require oxygen for metabolism. Instead their metabolic functions are dependent on a certain enzyme. Nano silver’s effect is primarily to disable this enzyme, hence it affects only pathogens including bacteria, viruses, fungi, germs and more,” says Stefanov.

He explains that regular use of such a spray on coils and filters of indoor and air handling units (AHU) improves overall indoor air quality, with the following benefits:

  • Aids in relieving respiratory conditions – allergies, asthma and cough
  • Eliminates and destroys airborne bacteria, viruses and dust mites
  • Non-toxic and safe for humans and pets
  • Environmentally friendly

Use of nano silver-based spray is highly recommended in the following facilities:

  • Health care facilities, applied on AHU coils and primary and secondary filters
  • Offices, especially open plan offices
  • Restaurants
  • Hotel rooms
  • Shopping malls
  • Individual households
  • Cars’ pollen/air filter

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