- Jul 2, 2003
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Do Surgical Masks Stop the Coronavirus?
Decent news about HEPA Filtration
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While particulate matter or organisms of any size can cause adverse effects to our health, particles below 2.5 microns in size are especially dangerous. These are small enough to be absorbed directly into our bloodstream and enter our lungs, heart, and brains.
Later investigations confirmed the existence of a minimum filterable particle size, but it has been found to be closer to 0.1 mm for the flow rates and paper compositions in use for currently manufactured nuclear grade HEPA filters [4]. Langmuir's theory affected u.S. filter technology
It seems counterintuitive that 0.3 micron particles would be harder to capture than 0.01 microns (30 times smaller). That is because we think of filters like a net, thinking that if a particle is smaller than the holes in the net, it gets through. That is how HEPA filters or N95 masks work for particles >0.3 microns.
These particles either cannot fit through, either because they are bigger than the filter hole size, or their inertia causes them to hit the filter fibers (impaction & interception).
Particles under 0.3 microns have so little mass the actually bounce around like pinballs when they hit gas molecules, so they move in random zigzag patterns. This is known as Brownian Motion. Here’s why that 0.3 micron number comes up all the time. The weirdness of Brownian motion happens under 0.3 microns.
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(A human hair is roughly 100 microns in diameter.) Human coronaviruses measure between 0.1 and 0.2 microns, which is one to two times below the cutoff.
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Airlines
Modern airliners use HEPA filters to reduce the spread of airborne pathogens in recirculated air. Critics have expressed concern about the effectiveness and state of repair of air filtering systems, since they think that much of the air in an airplane cabin is recirculated.
Almost all of the air in a pressurized aircraft is, in fact, brought in from the outside, circulated through the cabin and then exhausted through outflow valves in the rear of the aircraft.
Decent news about HEPA Filtration
===================================================
While particulate matter or organisms of any size can cause adverse effects to our health, particles below 2.5 microns in size are especially dangerous. These are small enough to be absorbed directly into our bloodstream and enter our lungs, heart, and brains.
.Regular HEPA filters are fantastic at capturing particles under 0.3 microns.
In fact, smaller particles, like 0.01-micron particles are even easier to capture than 0.3 micron particles
Later investigations confirmed the existence of a minimum filterable particle size, but it has been found to be closer to 0.1 mm for the flow rates and paper compositions in use for currently manufactured nuclear grade HEPA filters [4]. Langmuir's theory affected u.S. filter technology
It seems counterintuitive that 0.3 micron particles would be harder to capture than 0.01 microns (30 times smaller). That is because we think of filters like a net, thinking that if a particle is smaller than the holes in the net, it gets through. That is how HEPA filters or N95 masks work for particles >0.3 microns.
These particles either cannot fit through, either because they are bigger than the filter hole size, or their inertia causes them to hit the filter fibers (impaction & interception).
Particles under 0.3 microns have so little mass the actually bounce around like pinballs when they hit gas molecules, so they move in random zigzag patterns. This is known as Brownian Motion. Here’s why that 0.3 micron number comes up all the time. The weirdness of Brownian motion happens under 0.3 microns.
====================================================
(A human hair is roughly 100 microns in diameter.) Human coronaviruses measure between 0.1 and 0.2 microns, which is one to two times below the cutoff.
======================================================
Airlines
Modern airliners use HEPA filters to reduce the spread of airborne pathogens in recirculated air. Critics have expressed concern about the effectiveness and state of repair of air filtering systems, since they think that much of the air in an airplane cabin is recirculated.
Almost all of the air in a pressurized aircraft is, in fact, brought in from the outside, circulated through the cabin and then exhausted through outflow valves in the rear of the aircraft.