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Controlling airborne infections in poorly ventilated indoor spaces

Dilip Patil, Managing Partner, Trivector Biomed LLP uses his biomedical engineering expertise to explain how NanoStrike plasma technology can and should be used to protect the indoor air quality of poorly ventilated spaces.

Scientific as well as anecdotal reports indicate that the spread of airborne Covid microbes mainly occurs in closed indoor spaces. When an infected person, who may or may not be symptomatic, talks, coughs or even walks, he releases microbe-containing droplets called aerosols. Sometimes, these tiny droplets dry off and become droplet-nuclei. They remain in the air for a long period of time and travel a long distance. Any individual breathing this air is at risk of getting infected.

The second wave of Covid had reports of entire families being affected. This clearly indicates that airborne infections spread faster in closed indoor spaces. In open areas or areas with good natural cross-ventilation, these infectious droplets get pushed out (diluted) by the flow of air, minimising risk.

Due to tropical climate, polluted outside air, noise pollution and security risks etc., in India, it may not always be possible to keep the windows and doors open for natural ventilation. The existing buildings are normally designed to provide occupants with a comfortable environment (e.g. controlled temperature and humidity), but they don’t account for the risk of indoor pollution. We have closed, air-conditioned spaces in offices, hospitals, malls, theatres, schools, gyms etc, which are at higher risk of spreading infections.

Are existing solutions adequate?

Most of these closed (mostly crowded) spaces do have some form of ventilation but by the time the air is ‘cleaned’, they could have spread infections. There is a growing trend of using ACs (window/split) for smaller closed spaces. They mostly recycle the room air and bring in little fresh air. Larger spaces use expensive centralised duct-based HVAC systems with AHUs.

Depending upon the size of the room and the kind of HVAC system used, the total air in the room gets replaced with (presumably) fresh outside air. The number of air changes per hour (ACH) varies between 6-12 ACH in contrast to nearly 50-60 ACH in rooms with natural cross-ventilation.

Thus, even with existing air handling systems, the stale, possibly contaminated air laden with carbon dioxide remains in the room for longer duration. If the room is crowded, the risk of getting infected is even higher. In large complexes, the duct-based air cleaning system interconnects multiple rooms, so infectious particles from one room can go to another area, rapidly amplifying the spread of infections.

The regular cleaning of ducts and replacement of filters is paramount; if not maintained properly, the ducts and HEPA filters could themselves become colonised by bacteria and become a source of infection. These duct-based AHUs consume huge amounts of electricity, making the life-cycle cost of the system even higher.

Innovative air purification is the need of the hour

There is a need to complement existing air-cleaning methods with stand-alone in-room air disinfection units which can run continuously and quickly remove infectious particles from the air. The released air should be without any harmful side-effects of the discharge (e.g. positive or negative ions, free radicals, ozone, etc) and be safe to be consumed by the occupants of the room, to reduce the risk of spread of infection.

The air-disinfection units must be easy to install and operate, silent in operation, portable, mountable on wall, desk or ceiling, preferably in the breathing zone of the occupant and should need negligible maintenance. They should not harm the environment and consume minimal electric power to make them viable for 24X7 use.

The solution

NanoStrike (low-energy plasma – the fourth state of matter) is an active air disinfection technology patented and manufactured by the Irish company Novaerus, brought to India by Trivector Biomed LLP.

How does it work?

The device contains dielectric barrier diode (DBD) plasma coils with voltage applied to its electrodes to generate plasma at room temperature and atmospheric pressure. Room air, presumably with infectious particles, is drawn inside the device with the help of a multi-speed fan, and passes through the plasma field. Within nanoseconds, multiple concurrent inactivation processes (bombardment of charged particles, heat and UV radiation, electroporation by electromagnetic fields and cell bursting via osmotic pressure) in a single pass, destroy the airborne pathogens, viruses, bacteria and fungi.

The microbes are directly exposed to plasma rather than the by-products of plasma, as the air flows through the coils. Once the air flows over the coils; the DNA/RNA, protein and other cellular organelles of the microbes – without any discrimination – get destroyed in a single strike, without giving microorganisms an opportunity to reconstruct or multiply.

Tested, validated and certified by US-FDA, CE, ISO, UL etc., NanoStrike technology takes care of shortcomings of all existing air purification methods and enhances their utility further to provide the most sustainable solution for air-borne infection control.

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