Preventing the accumulation of viruses in indoor environments represents a major community health challenge. The recent COVID-19 pandemic, sustained by the SARS-CoV-2 virus, highlighted the role of confined spaces and indoor air quality for public health. Not surprisingly, people spend much of their time indoors, where air quality is crucial to limiting infection risks.
In the following paragraphs, we will focus on respiratory viruses and the factors that influence their risk. We will then examine strategies to reduce infection risks in confined spaces, with a specific focus on air quality.
Risks in Indoor Spaces
Originating from infected individuals, expelled into the environment through coughing and sneezing, respiratory viruses accumulate as bioaerosols in indoor air, where they can remain suspended for many hours. This is especially true in poorly ventilated spaces, which significantly affect the spread of infectious diseases.
As noted earlier, people carry out most daily activities indoors for professional, family, or leisure reasons. For this reason, indoor air quality can directly affect health, as well as perceived well-being and productivity. Particularly in the post-pandemic era, assessing indoor air quality has become an essential part of evaluating workplace-related infection risks.
Viral Transmission and Contributing Factors
Environmental factors such as relative humidity and temperature play a key role in viral efficiency—that is, infectivity, survival in the environment, and transmission levels. They can also impair human respiratory defenses, particularly by hindering proper mucociliary clearance.
Targeted studies on SARS-CoV, SARS-CoV-2, and MERS-CoV report that relative humidity levels between 40% and 50%, combined with temperatures between 20°C and 25°C, help preserve viral viability. On the other hand, other data suggest that temperatures above 30°C and relative humidity not exceeding 78% may reduce SARS-CoV-2 transmission.
Regarding influenza viruses, research shows efficient transmission at low temperatures (around 5°C), while 30°C is unfavorable. In the same study, low humidity levels (20%–35%) were associated with higher viral spread compared to higher humidity.
In essence, keeping these parameters within well-defined ranges is desirable to reduce viral transmission potential indoors.
Classic and Innovative Solutions
Innovative solutions developed over time coexist with older, simple, and intuitive strategies. These approaches can complement one another, supporting safer indoor use.
Non-technological Strategies Against Viruses
- The first measure to prevent viral infections is physical distancing from potentially infected individuals (recognizable by respiratory symptoms). Widely applied during the COVID-19 pandemic, distancing proved effective in reducing viral transmission in both hospital settings and crowded non-healthcare environments.
- Face masks, another prominent measure during the pandemic, are a non-technological but common-sense solution against respiratory viruses. According to scientific studies, proper mask use can reduce infection risk up to tenfold. Masks are best combined with other protective measures such as distancing or air purification.
- A conventional but effective measure to reduce viral concentrations and improve indoor air quality is ventilation. This can be achieved naturally by opening windows and doors to allow air exchange.
Technological Innovations for Indoor Health
- When natural ventilation is not possible (e.g., absence of windows) or not practical (e.g., external temperatures unsuitable for frequent exchange), mechanical ventilation (CMV) is an effective alternative. It extracts stale indoor air and introduces fresh air from outside, often with integrated monitoring of humidity, temperature, and CO₂ levels.
- HEPA filters (High Efficiency Particulate Air) provide advanced air purification, retaining up to 99.995% of airborne contaminants, including viruses in bioaerosols. Studies confirm their high effectiveness, especially in poorly ventilated spaces (source).
- UV-C radiation is another proven method to inactivate viruses in indoor air. Combining UV-C with good air circulation is considered more effective than relying on stronger lamps alone. Research shows that ventilation combined with UV-C successfully reduced SARS-CoV-2 indoors.
- Devices based on the neutralizing power of microwaves are also noteworthy, as we will see in the next section.
The Effectiveness of Magnetic Wave Devices
Viral neutralization using microwaves is based on vibrational resonance mechanisms. Devices emit microwaves at specific frequencies, causing mechanical stress in viral particles. As a direct result, they damage viral envelopes and compromise pathogen integrity. Effectiveness depends on the viral type, the frequency applied, and exposure time.
Compared to other technologies, microwave devices are harmless to humans while offering high neutralization capacity. Widely applied across industries and households, microwaves are effective in microbial inactivation across various substrates, including water and food. In air purification, this approach can complement other inactivation strategies, such as UV radiation.
Devices developed by e4life generate oscillating electromagnetic fields that inactivate airborne viruses almost instantly, achieving over 90% effectiveness. They fall under non-chemical sanitation strategies and are suitable for different contexts, including applications in livestock farming. Overall, this technology reflects the One Health philosophy, aimed at human and animal well-being within a healthy environment.