[MUSIC PLAYING]
COVID-19 is a respiratory disease
caused by the transmission of the virus SARS-CoV-2.
The primary mechanism of transmission
is through aerosol particulates from mucus or saliva
that contain the virus and are emitted
during breathing, talking, singing, coughing, or sneezing.
MIT Lincoln Laboratory conducted a study
to investigate how aerosols are dispersed and potential
mitigation techniques in mass transit vehicles.
The objective was to determine how changes in the operating
conditions of the vehicle affected how aerosols
are dispersed inside the vehicle so that transit operators could
determine actions to lower the risk of infection to occupants.
We aerosolized a safe liquid in a way that
mimicked a person coughing and a variety of sensors
were distributed throughout the vehicle.
To measure the size and the number of aerosols
detected at each location over time.
A critical operating condition investigated
was how a vehicle's air filtration system affected
the aerosol dispersion.
Not all air filters are created equal.
They're categorized by filtration efficiency ratings,
also known as MERV ratings.
Depending on what size aerosols they can filter effectively
from the air.
For example, common MERV 8 or 9 filters
can efficiently remove most pollen and other very large
particles.
Unfortunately, an infected person
can emit aerosols containing SARS-CoV-2
in a wide range of sizes from hundreds of microns, which
is the width of a human hair, down to tens of nanometers
or 10 times smaller than a single red blood cell.
These smaller respiratory aerosols
require higher efficiency MERV ratings, such as MERV 13
or higher, in order to increase the likelihood of removing
the SARS-CoV-2 laden aerosols.
The trade off is that these higher efficiency
filters are also costlier and typically slow
down air movement.
We can apply several aspects of this study
to help solve another related problem.
How to obtain clean water by creating a water filtration
system?
One of the most important things to understand
before creating a solution to any problem
is the requirements.
What problem are we trying to solve?
How efficient does this filtration system need to be?
How large or small must it be?
What is the budget?
How much time do we have to complete this project?
After determining the requirements,
we can start to build a team and define tasks.
To have a successful team, it is important to have team members
with the correct types of expertise and a clear roadmap
to fulfill these requirements, accompanied
by well-defined tasks and roles.
When thinking about how to build a water filtration system,
consider the trade offs that each material or component
may have.
For our study, one key trade off was between filtration
efficiency and airflow.
When trying to remove sediments from water with your filtration
system, a wire mesh may allow water
to exit the filter at a higher flow rate,
but may only capture the larger granular particles.
On the other hand, a cotton ball may remove finer sediments
but may have a slower flow rate.
As you can imagine, there may be several options or combinations
of options that can solve the same problem.
Determining which options would create a water filtration
system that meets all of the requirements,
considering the constraints and trade
offs of size, time, and budget, are all part
of the fun in engineering.