Virus Aerosol Research

We know that infected people generate and release droplets and aerosols by coughing, breathing, speaking, etc. Others who have contact with these droplets or aerosols may risk infection. Determining the exposure and infection risk for these individuals raises many questions. For example: 

• How do these particles spread in a room? 
• How does the air circulation in the room affect how far these particles can travel from the point of release? 
• How does the size distribution of the particles affect the dispersion and spread of the aerosol cloud? 
• What is the viral content and its viability within the aerosol droplets or particles? 

For years, our research customers have found TSI particle instruments to be valuable experimental tools in addressing questions like these.

The Evolution of Human-Generated Aerosols

Aerosols emitted by people when breathing, talking, sneezing, and coughing are liquid droplets. Because outside air is usually not as humid as the air inside a human respiratory system, the droplets begin to evaporate soon after emission. Evaporation shrinks them, which affects how far they can travel. 

The largest droplets settle onto the floor or other surfaces, due to gravity. The remainder stay airborne for some time, depending upon their final size after evaporation is complete. Droplets eventually become tiny solid particles that may contain viable microorganisms, including viruses. The smaller the particles are, the longer they can stay suspended in air, and the better they are able to spread over longer distances. We know that very small droplets and particles are able to deposit deep into the respiratory tract. Size, distribution, and concentration are particle characteristics that are relevant to the above research questions. Consequently, it’s vital to be able to measure these characteristics accurately. 

Aerosol Size Distribution Measurements

Sizing Solutions for 1 Micrometer and Larger

For measuring particles in the 0.5 to 20 µm range, the Aerodynamic Particle Sizer™ (APS™) 3321 spectrometer is a field-proven instrument. It uses a robust ‘time of flight” technique that determines the aerodynamic particle diameter, a parameter that is commonly used to characterize the deposition of particles in the human respiratory system. The APS™ 3321 spectrometer is used by numerous governmental, academic, and military laboratories around the world to measure aerosols emitted by the human respiratory system.

The Optical Particle Sizer (OPS) 3330 is another instrument that can measure airborne particles in the 0.3 to 10 µm size range, but with a lower size resolution compared to the APS™ 3321. This spectrometer uses a light-scattering technique to provide a response that is dependent on the refractive index of the measured particles. For example, the illustration below shows an experimental setup using TSI instruments. In this experiment, researchers sought to measure the size distribution and concentration of aerosol particles emitted by a person during coughing events. 

Sizing Solutions for Sub-Micron Particles

For measuring particles in the 1 – 1000 nm size range, TSI offers instrument that utilize the electrical mobility of particles to determine their size, and then follow that size-selection aspect with a particle counter. The Scanning Mobility Particle Sizer™ (SMPS™) spectrometer is configurable to measure different size ranges depending on the specific application; they have excellent sizing resolution and particle concentration range. The SMPS™ 3938 spectrometers made by TSI are serving worldwide in academia and industry for a variety of applications, including virus characterization studies.

Every day, TSI helps researchers answer important questions and reach their goals. How can we help you advance knowledge in your field?

Learn More About Aerosol Research