The weather has started to get cold and for some people that means it’s time to turn on more indoor fans.
Does it sound strange? You bet. But COVID-19 has clouded just about everything else, so why not indoor ventilation habits?
The idea is to create your own virus trap by placing a filter in front of a case fan somewhere in the room or by purchasing a mobile ventilation unit with specialized filters, like the R2D2 with a medical degree. Eventually the thought goes, floating chunks of aerosol moisture from everyone’s breathing will be sucked in and trapped with all the COVID viruses they contain.
Blocking airflow on an electric motor is usually not a good decision, so the EPA tested the filter and fan configuration to make sure it was not a risk of fire, spurred by their increasing use to prevent fire smoke from escaping. of outbreaks in the West. No worries, they said in a press release: “Fan temperatures have remained below safety standards and no tests have revealed any observable fire hazards. ”
They are therefore safe. But are they effective?
There is no doubt that ventilation is the key to maintaining a healthy indoor space. This is why HVAC (“heating, ventilation, air conditioning”) systems have filters. The Concord School District, for example, has over 1,000 filters in all furnaces and fans in its schools and other buildings, and they are all changed quarterly.
The Centers for Disease Control is placing ventilation at the center of its recommendations for controlling COVID-19 indoors. But there is a catch.
I will quote the CDC website: “The room described in Example 2 is now completed with a portable HEPA air purifier with a smoke CADR of 120 cfm (Qhepa = 120 cfm). The extra air movement in the room improves the overall mixing, so assign k = 3. Question: How much time is saved to achieve the same 99% reduction in airborne contaminants by adding the portable HEPA device? piece ? ”
If the system is not large enough, not moving enough air, there is no guarantee that the room is much safer.
This is especially true because the movement of air is very complicated. This is an example of fluid dynamics, a subject so thorny that it makes physics students cry and they change their specialization in psychology.
Unless you hire a professional to perform smoke tests or blast tests to determine how the air actually moves in a room, there is no guarantee that all air, or even a most of it, will pass through your device and be cleaned. It feels good to plug a MERV16 bungee filter into a box fan you took out of the garage and put it on a handy table, or have a mobile fan unit flashing in a corner where people won’t hit it, but that’s no guarantee.
The caution poster child occurred in May in California when an unvaccinated teacher who was showing symptoms pulled down her mask to read to a class and ended up infecting 12 of her students who were all fully masked – although the room had windows open on both sides plus “high efficiency portable particulate air filters”.
The result of all this is that we are working by all means to improve the ventilation in our homes and offices or businesses. But we have to be careful not to kid ourselves that it’s a substitute for all the other COVID-19 guarantees we need: vaccination, masking in crowds, basic sanitation.
And get vaccinated – did I mention getting vaccinated? Don’t forget that one.
For coronavirus information and updates throughout the week, visit concordmonitor.com/coronavirus.
How do we go about the vaccinations? Maybe a slight increase, but a very small one.
The state’s tally of the number of state residents fully vaccinated each week peaked in April at nearly 10,000 and steadily declined through July to less than 300 per week, which is next to nothing in a state of 1.35 million people.
Since the beginning of September, the weekly count has gone from 140 to almost 180 per week. It’s still painfully low, but it could indicate that corporate vaccine requirements are starting to have an effect.
In general, however, there’s always a 45% chance that a New Hampshire resident you meet will not be vaccinated. Keep that in mind.
What is the trend on the spread and impact of the disease? Not good, but not worse.
State data clearly shows that we are in a slightly worse situation as we were at the peak of the second surge in April.
Currently, the daily number of new cases has averaged 455 over the past two weeks, up from a high of 434 in April; there are 144 people in hospital with COVID-19 compared to a peak of 133 in April; and almost exactly 2 people die each day on average compared to 1.6 in April.
On the flip side, none of those numbers have increased over the past week, although temperatures have caused us to stay more indoors, so we may have hit a new high. Maybe the vaccination will prevent a copy from last winter when it all got worse in December and much worse in January.
(David Brooks can be reached at 369-3313 or [email protected] or on Twitter @GraniteGeek.)