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The cabin air is about half recirculated, half fresh air from the engines. But the recirculated air is filtered. An N95 mask can filter >95% of .3 micron partic

The cabin air is about half recirculated, half fresh air from the engines. But the recirculated air is filtered. An N95 mask can filter >95% of .3 micron particles, this cabin air filter can capture 99.9%. https://www.ptitechnologies.com/news-event/pti-announces-the-introduction-of-cabin-air-filters/ https://www.ptitechnologies.com/news-event/pti-announces-the...

always_left 6y ago
To put it in perspective, air plane air filters are almost as good as surgical rooms :)
ikeyany 6y ago
Are these in operation the entire time passengers are on the plane, or only when the engine is on?
- KMag 6y ago
  They either idle the engines / run the APU to keep air circulating the whole time, or else they pipe in fresh air. I think it's SeaTac airport where they paint a message about "Mister Pipe" or "Mister Air Pipe" right on the jetway air pipe, along with a message about how it reduces pollution by reducing engine / APU idling, ending with "Thank You, Mister [Air?] Pipe". This "pipe" allows the more efficient (and bulky / heavy) air filtration and industrial chillers in the airport to be used to supply fresh air to the plane while the jetway is extended. If this weren't the case, the plane would get very stuffy very quickly. Imagine your share of the cabin space. Now imagine yourself sealed in a cardboard box that size waiting for the plane to board. How many minutes before your cardboard box becomes unbearable? They're always pumping in fresh air while passengers are in the airplane.
  - deleted 6y ago
    [deleted]
  - ikeyany 6y ago
    But planes do get stuffy very quickly, especially when they don't turn on the engine for a long time.
henvic 6y ago
HEPA filters really help you get pristine air quality. Large commercial buildings and aircraft have them. More expensive cars, sometimes. For homes, I think most people don't have it. However, I imagine it might be more popular in some colder areas with central A/C units. I have purchased two Philips purifiers... In October, I bought the AC3259. We use it in the bedroom. It's great, and you can use the Air Matters application on your phone to see how the air quality of your place is. At the end of March, I bought the Philips AC3829/10. It's a purifier + humidifier unit and is more practical, and I use it in the living room. Our apartment is only about 78 square meters, so using both is a little overkill, but we have a fluffy dog, so definitely, it's making a difference to our health. We (two people + dog) spent most of the time in the living room these days, and we have to clean the purifier in the bedroom every day, but the one in the living room only about a week or so. I'd recommend getting a large purifier with a HEPA filter to anyone concerned about their health these days.
- ornornor 6y ago
  AFAIK, home air purifiers are just theatre. 1. There is no way you’re getting a right seal all the way through the purifier because if you did it would cost orders of magnitude more. So there is air being sucked in around the filter and along the way that mixes with the filtered air 2. I seem to remember virus (and smells or VOCs) are way too small to be caught by a hepa filter so they just float right through 3. Some filters have a uv light in them. But they’re inefficient because not all the air is exposed, the exposition duration is too short, and it generates ozone as a side effect (probably not great to breath in large quantities) 4. They do an ok job at catching dust particles for allergy sufferers and some of the pollen
  - henvic 6y ago
    I'm surprised you are saying a purifier with a HEPA filter might be this bad. Orders of magnitude more? Are we talking about the same category of products? What is your source saying HEPA filter doesn't filter viruses? Do you any data to back up your claims? Regarding UV light, I agree that it might not be too effective... (but I had a great experience with using one on my aquarium a long time ago).
elhudy 6y ago
Why do I get allergy attacks about 50% of the time on planes, without fail, if the air is so well filtered :(?
- quickthrowman 6y ago
  The relative humidity of air in an airplane is low, usually under 20%. Upper respiratory irritation is caused by more than just allergies.
  - elhudy 6y ago
    That's.... Something I've never even considered. Thank you for pointing that out. I wonder if the pressure difference adds to the irritation as well.
Yizahi 6y ago
Yes, it is recirculated. The question is - does it happens with air speed 100-200 m/s like in wind tunnel so that any particles are evacuated directly from a passenger to the vent? Or maybe it happens extremely slowly and each cough spreads just like in a room, several meters around coughing person and persists for multiple minutes before being drawn to the vent? The answer is obvious.

always_left 6y ago

To put it in perspective, air plane air filters are almost as good as surgical rooms :)

ikeyany 6y ago

Are these in operation the entire time passengers are on the plane, or only when the engine is on?

KMag 6y ago
They either idle the engines / run the APU to keep air circulating the whole time, or else they pipe in fresh air. I think it's SeaTac airport where they paint a message about "Mister Pipe" or "Mister Air Pipe" right on the jetway air pipe, along with a message about how it reduces pollution by reducing engine / APU idling, ending with "Thank You, Mister [Air?] Pipe". This "pipe" allows the more efficient (and bulky / heavy) air filtration and industrial chillers in the airport to be used to supply fresh air to the plane while the jetway is extended. If this weren't the case, the plane would get very stuffy very quickly. Imagine your share of the cabin space. Now imagine yourself sealed in a cardboard box that size waiting for the plane to board. How many minutes before your cardboard box becomes unbearable? They're always pumping in fresh air while passengers are in the airplane.
- deleted 6y ago
  [deleted]
- ikeyany 6y ago
  But planes do get stuffy very quickly, especially when they don't turn on the engine for a long time.

henvic 6y ago

HEPA filters really help you get pristine air quality. Large commercial buildings and aircraft have them. More expensive cars, sometimes. For homes, I think most people don't have it. However, I imagine it might be more popular in some colder areas with central A/C units. I have purchased two Philips purifiers... In October, I bought the AC3259. We use it in the bedroom. It's great, and you can use the Air Matters application on your phone to see how the air quality of your place is. At the end of March, I bought the Philips AC3829/10. It's a purifier + humidifier unit and is more practical, and I use it in the living room. Our apartment is only about 78 square meters, so using both is a little overkill, but we have a fluffy dog, so definitely, it's making a difference to our health. We (two people + dog) spent most of the time in the living room these days, and we have to clean the purifier in the bedroom every day, but the one in the living room only about a week or so. I'd recommend getting a large purifier with a HEPA filter to anyone concerned about their health these days.

ornornor 6y ago
AFAIK, home air purifiers are just theatre. 1. There is no way you’re getting a right seal all the way through the purifier because if you did it would cost orders of magnitude more. So there is air being sucked in around the filter and along the way that mixes with the filtered air 2. I seem to remember virus (and smells or VOCs) are way too small to be caught by a hepa filter so they just float right through 3. Some filters have a uv light in them. But they’re inefficient because not all the air is exposed, the exposition duration is too short, and it generates ozone as a side effect (probably not great to breath in large quantities) 4. They do an ok job at catching dust particles for allergy sufferers and some of the pollen
- henvic 6y ago
  I'm surprised you are saying a purifier with a HEPA filter might be this bad. Orders of magnitude more? Are we talking about the same category of products? What is your source saying HEPA filter doesn't filter viruses? Do you any data to back up your claims? Regarding UV light, I agree that it might not be too effective... (but I had a great experience with using one on my aquarium a long time ago).

elhudy 6y ago

Why do I get allergy attacks about 50% of the time on planes, without fail, if the air is so well filtered :(?

quickthrowman 6y ago
The relative humidity of air in an airplane is low, usually under 20%. Upper respiratory irritation is caused by more than just allergies.
- elhudy 6y ago
  That's.... Something I've never even considered. Thank you for pointing that out. I wonder if the pressure difference adds to the irritation as well.

Yizahi 6y ago

Yes, it is recirculated. The question is - does it happens with air speed 100-200 m/s like in wind tunnel so that any particles are evacuated directly from a passenger to the vent? Or maybe it happens extremely slowly and each cough spreads just like in a room, several meters around coughing person and persists for multiple minutes before being drawn to the vent? The answer is obvious.