Airborne Transmission Dynamics in Indoor Environments

Airborne transmission in indoor settings arises from the emission, transport and inhalation of respiratory particles that span a continuum from large droplets to fine aerosols. Exhaled particles are generated during breathing, speaking, coughing and singing, with their subsequent behaviour governed by size, environmental conditions and airflow patterns. Larger droplets settle rapidly, contaminating surfaces and contributing to short-range transmission, while smaller aerosols can remain suspended for minutes to hours, disperse throughout enclosed spaces and pose an inhalation risk at greater distances. The evaporation of droplets under varying temperature and humidity alters particle size, creating droplet nuclei that extend airborne lifetime. Ventilation, air filtration and ultraviolet disinfection are among the principal engineering controls designed to dilute or inactivate pathogen-laden aerosols. Understanding the multiphase flow mechanics of droplet release, the influence of occupant behaviour and the efficacy of mitigation measures is essential for evidence-based guidance on occupancy limits, mask usage and building design, all of which bear on global strategies to reduce respiratory disease spread in schools, offices, healthcare facilities and public transport hubs.

Research from Nature Portfolio

Recent studies have characterised the role of speech in aerosol generation, demonstrating that vocal loudness correlates with particle emission rates and identifying a subset of individuals as “superemitters” who release substantially more aerosols than average. This work underscores how variation in human physiology and vocal effort can drive superspreading events and highlights the need for tailored mask policies in shared environments. Investigations of far-UVC light (207–222 nm) have shown that low-dose, continuous exposure can inactivate over 99 per cent of aerosolised coronaviruses within minutes, while remaining safe for skin and eyes. This technique offers a prospective disinfection strategy for occupied spaces without interrupting normal activities. Concurrent environmental sampling in patient rooms has revealed the presence of virus-containing particles in both >4 µm and 1–4 µm size ranges despite high air-change rates, reinforcing the importance of airborne precautions and real-time monitoring to guide isolation protocols.

Airborne Transmission Dynamics in Indoor Environments publication trend

The graph below shows the total number of articles in airborne transmission dynamics in indoor environments across all publications each year (not limited to Nature Index journals).

Technical terms

Aerosols: Airborne particles smaller than 5 µm that can remain suspended and be inhaled deeply into the respiratory tract.

Droplet nuclei: Residual particles formed after evaporation of larger respiratory droplets, typically 1–10 µm in diameter.

Superemitter: An individual who consistently produces respiratory particles at rates significantly above the population average.

Ventilation rate: The volume of outdoor or filtered air supplied to an indoor space per unit time, usually expressed in air changes per hour (ACH).

Far-UVC: Ultraviolet light in the 207–222 nm band that inactivates airborne pathogens while posing minimal risk to human skin and eyes.

References

1. On-site airborne pathogen detection for infection risk mitigation. Chemical Society Reviews (2023).
2. Mechanisms controlling the transport and evaporation of human exhaled respiratory droplets containing the severe acute respiratory syndrome coronavirus: a review. Environmental Chemistry Letters (2023).
3. Aerosol emission and superemission during human speech increase with voice loudness. Scientific Reports (2019).
4. Early Release - Aerosol and Surface Distribution of Severe Acute Respiratory Syndrome Coronavirus 2 in Hospital Wards, Wuhan, China, 2020 - Volume 26, Number 7—July 2020 - Emerging Infectious Diseases journal - CDC. Emerging Infectious Diseases (2020).
5. The airborne lifetime of small speech droplets and their potential importance in SARS-CoV-2 transmission. Proceedings of the National Academy of Sciences of the United States of America (2020).
6. Airborne transmission of respiratory viruses. Science (2021).
7. Recognition of aerosol transmission of infectious agents: a commentary. BMC Infectious Diseases (2019).
8. Far-UVC light (222 nm) efficiently and safely inactivates airborne human coronaviruses. Scientific Reports (2020).