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  • (anxious music)

  • - [Reporter] Take a look at this map.

  • It shows the change in coronavirus cases

  • over the past two months.

  • You can see cases arising.

  • And as the weather gets colder and people had back indoors,

  • experts say it could get worse.

  • - As we get through the fall and into the winter

  • with the holiday season going,

  • we've got to do something different.

  • - [Reporter] Experts warn that many buildings,

  • like restaurants, schools, and homes,

  • are not equipped with the ventilation and filtration systems

  • needed to reduce the spread of COVID-19.

  • - So, by now, people are really familiar

  • with masking, hand-washing, distancing,

  • but fewer people are aware that ventilation

  • and filtration really matter.

  • - [Reporter] It's now clear that the coronavirus

  • travels through the air,

  • which is why indoor gatherings can be so deadly.

  • The virus can accumulate in aerosols,

  • tiny droplets that gather in the air,

  • as we breathe and talk.

  • - That virus is never naked in the air, is what we say.

  • It's always floating in respiratory droplets

  • that are much bigger.

  • - [Reporter] Indoors, those particles can add up,

  • increasing the risk of transmission.

  • And one way to mitigate that

  • is to pump in fresh air with a ventilation system.

  • - We have to think about the thermal conditions

  • like humidity and temperature,

  • but also just how much outdoor air is moving in.

  • For me, the priority is to increase the air exchange rate.

  • - [Reporter] The air exchange rate

  • determines how many times an hour

  • fresh air circulates through a building.

  • There's not an exact recommended rate,

  • but experts say that three to six exchanges per hour

  • is ideal.

  • But good flow of fresh air is only one part

  • of preventing the indoor spread of the coronavirus.

  • The other is filters,

  • and experts recommend using one called HEPA.

  • This type of pleated mechanical filter

  • is made from fiberglass, foam or cotton.

  • It can remove more than 99% of airborne particles,

  • including those carrying viruses like the coronavirus.

  • This is the same type of filter

  • used in hospitals and airplanes,

  • but there has been some confusion

  • over whether or not HEPA filters

  • can effectively capture airborne coronavirus.

  • That's because these filters are rated for particles

  • that are 0.3 microns in size, larger than the coronavirus.

  • People assume that they don't catch anything smaller,

  • but that's just not true.

  • - Filters are rated for the particle size

  • they perform worst at, and that's 0.3 microns.

  • As you get to bigger particles, and even smaller particles,

  • the HEPA filter will capture closer to 100%.

  • - [Reporter] Because the coronavirus tends to travel

  • in droplets that are larger than 0.3 microns,

  • HEPA filters can capture almost all of them.

  • The virus also travels in droplets that are smaller,

  • and HEPA filters can capture those too.

  • - Filters work not by straining out things

  • that are larger than the holes in them,

  • but they actually work by trapping particles in the air

  • as the air flows around the different fibers in the filter.

  • - [Reporter] When very small aerosols

  • bump into gas particles, they move in a random pattern.

  • That is called Brownian motion.

  • - Kind of like a drunk person stumbling around in the dark.

  • And because of that random motion,

  • they can crash into the fibers.

  • - [Reporter] The harder it is for particles

  • carrying viruses to pass through a filter,

  • the lower the chance of viral transmission.

  • But the problem is that not every building

  • has a system that can handle them.

  • - When you have a air system moving air

  • through the building, and then it runs through a filter,

  • you can imagine that a higher-efficiency filter

  • that's more tightly woven

  • is going to be harder to push air through.

  • Very few systems can push air through a HEPA filter

  • unless it's designed that way,

  • because HEPA is the most efficient filter we have.

  • - [Reporter] That is why experts recommend

  • that schools, businesses and homes

  • use a different type of lower-efficiency filter called MERV.

  • - If you can get up to something called MERV-13,

  • that's able to remove 80% or more

  • of viruses that might be in the air.

  • - [Reporter] This is important because this type of filter

  • can be installed in standard ventilation systems,

  • like what you might have in your home.

  • Still, there are plenty of buildings

  • that aren't able to adapt this type of filter either.

  • - Many people are starting to realize for the first time

  • that their buildings can't respond.

  • Their systems are not dynamic, they're not resilient,

  • they can't increase capacity.

  • - [Reporter] Older and underfunded schools

  • face some of the biggest challenges.

  • According to the U.S. Government Accountability Office,

  • 41% of districts need to update or replace

  • their ventilation system in at least half of their schools,

  • which adds up to about 36,000 schools nationwide.

  • The Washington D.C. public school system

  • spent $24 million on upgrades

  • to handle higher-efficiency filters

  • in preparation for the return of students and teachers.

  • And it's not just pricey for schools.

  • Some restaurants that will need to spend over $30,000

  • to upgrade their systems, in addition to operating costs.

  • - You pay more for energy

  • to bring in more outdoor air and condition it,

  • and also work harder, your system will work harder

  • to push air through a higher-efficiency filter.

  • - [Reporter] The air pumped into buildings

  • also needs to be cooled or heated,

  • which adds to energy bills.

  • Even though not every building

  • can afford to make these adjustments,

  • experts say there are other solutions.

  • For older buildings with outdated systems,

  • opening windows is a good, cheap option.

  • But in the winter, this isn't always possible,

  • and some buildings have windows that are sealed shut.

  • - If you can't hit the targets,

  • consider supplemental air cleaning

  • through the use of a portable air cleaner

  • with a HEPA filter.

  • Now, if you size these correctly for the room,

  • for restaurant, a school classroom, a bedroom at home,

  • you can get four, five or six air changes per hour

  • of clean air, and it can be cost-effective.

  • - [Reporter] That's what the DC public school system did,

  • in addition to upgrading their ventilation systems.

  • The bottom line, we know that the coronavirus

  • can spread through the air,

  • and we know how to reduce the risk of transmission.

  • The biggest hurdle will be the cost

  • of putting the science into action.

  • (bouncy sting music)

(anxious music)

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B1 US WSJ filter air reporter ventilation efficiency

Ventilation Is Key to Battling Covid. Here’s Why | WSJ

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    joey joey posted on 2021/05/31
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