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Comment by blip54321 | Hacker News Reader

General agreement.

One correction: Airplanes are safer than Costco.

When I first read the claims about air exchange rates on airplanes, I thought it was corporate propaganda. I looked at the research. Flying is authentically pretty safe. The air gets cycled and scrubbed insanely quickly. There's still a risk, but it's safer than Costco.

If you do need to travel, you want to be paranoid exactly at airports and similar. The flight itself is not so bad.

There was a flight a while back, where everyone wore masks (cloth or surgical) and had some crazy number of people with COVID on-board, but no in-air spread.

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> There was a flight a while back, where everyone wore masks (cloth or surgical) and had some crazy number of people with COVID on-board, but no in-air spread

Anecdotal but my friend had taken off his mask for 5 minutes for eating during a flight (this was during India's massive wave) and he got infected. Almost everyone would have been wearing a mask (unless eating themselves). Off course it's possible that masks are incredibly effective (and I'm not doubting that) but I'm not convinced aircraft filtration systems are that top tier.

I'm wondering how you/he was able to determine that he got infected during, rather than before or after the flight.

Because before that he was in his university's hostel that had cut off outside access for several weeks, and while he isolated after coming home he got sick about 4-5 days post his travel. Of course this is what he told me so there's some data loss but he emphasized heavily how he was practically always masked except for while eating.

Intuitively, it doesn't make sense to me. How do they scrub the microscopic particles containing sars-cov-2 and how do they recirculate my breath before it gets to the guy next to me?

They don't need to.

Omicron aside, peak infection rates were around 30 cases daily per 100k. The odds of the guy next to you having COVID were always very low. The odds of someone in the same building, airport, plane, bus, classroom, workplace, etc. having COVID were often quite high.

Airplane filtration systems mean you /only/ have to worry about the guy next to you, and not about everyone else on the airplane. That's pretty low risk.

The other curiosity about COVID are superspreaders. Most people don't spread COVID very much. A few people spread COVID /a lot/. The question isn't just whether you're sitting next to someone with COVID, but whether you're sitting next to a superspreader. If the person next to you has COVID, but isn't shedding a lot of virus, you're probably okay too.

That said, the guy next to you likely isn't shedding microscopic particles, but pretty large droplets. Your mask stops large droplets pretty well. The airplane filtration system just needs to get them before the become microscopic particles.

Planes don't really do much filtering, and air "recirculating" in a plane is largely a myth.

Rather, some of the air going into the big fans of the engines is diverted into some air conditioning machinery that gets it to a comfortable temperature and humidity, and then pumped into the passenger compartment. In order to maintain the correct pressure, there are basically "leakage" valves that let air flow out of the plane. An airplane maintains pressure by balancing how much air is allowed out of that valve vs how much air is coming in through the AC machinery. The result is the vast majority of air inside of a plane at any time is air that was previously outside the airplane.

> Rather, some of the air going into the big fans of the engines is diverted into some air conditioning...

To be pedantic, modern bleedless engines don't do this but just directly get fresh air :)

Sample size of one, but every.single.time I fly long haul, I get a cold.

While it is certainly possible you got sick on the airplane itself, don't factor out the trip to the airport (cab/public transit) and all the different crowds your have to deal with at the airport itself. I know airport staff do the best they can, but during particularly busy travel times airport bathrooms can be incredibly disgusting in my experience.

Aye, it's far from certain it's happening on the aeroplane itself, but I've assumed it is because the air is so dry, and because I was always travelling in business, using lounges with nice toilets, not being next to other people outside of the plane etc.

I think you are underestimating how often business class people are traveling slightly ill

Sample size of many, but correlations doesn't imply causation.

Evidence for limited spread on airplanes is pretty solid, but everything from here on out is speculatory:

* A lot of people get sick traveling. You're interacting with all sorts of people from far away who have novel viruses, many of which aren't circulating in your area. That doesn't mean you catch it literally on the airplane.

* Masks probably make a bigger difference on airplanes than elsewhere. Even cloth masks catch big particles. By the time droplets evaporate into small droplets, odds are they've passed through a HEPA filter many times.

If travel is stressful, or causes you to get less sleep, (etc) that may also affect your immune system.

In addition to the other responses, plane cabins have very low humidity, which can take out your mucosal protections from getting a cold. It's really common to at least have a scratchy throat after flying just from dryness, and often times catch a cold afterward.

Yes, I think this is probably what does it - my nose and throat always feel really dry after a long flight, actually I almost feel dehydrated.

Rhinoviruses spread not only via aerosols, but also supposedly spread better through surface contact than COVID19. Air circulation won't stop you from touching a contaminated surface.

But its pretty clear medicine has a very poor understanding about how viruses spread given how long they denied coronaviruses were airborne. So who knows.

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