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The straight dope on N95 masks and the H1N1 virus.

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MercutioATC Donating Member (1000+ posts) Send PM | Profile | Ignore Sat May-02-09 01:41 PM
Original message
The straight dope on N95 masks and the H1N1 virus.
There's been a lot of misinformation posted here claiming that N95 masks do not provide protection from the transmission of the H1N1 virus. While it's true that N95 masks do not provide complete protection, they are a valuable layer of defense.

Influenza viruses are usually transmitted in two ways, direct transmission (touching an infected surface) or droplet transmission. The influenza virus does not transmit across long distances and doesn't survive well when exposed to air (single influenza viruses don't just float around by themselves).

First, some numbers:

"N95" is a NIOSH standard, meaning that the mask stops 95% of particles .3 microns or larger in size.

The average influenza virus is about .12 microns in size.

The average sneezed/coughed droplet is over 10 microns in size.

The average droplet nucleus size is 5-10 microns in size.


Since influenza viruses don't just float around alone, we're dealing with protecting against airborne particles over 5 microns and direct contact with infected surfaces.

The N95 mask will ideally provide a barrier to 95% of the airborne droplets ("ideally", because anything but a perfect mask fit...which is impossible to achieve...will reduce that protection). It will also prevent one from touching their nose and mouth with infected hands.

This is why the CDC recommends wearing an N95 mask if one cannot completely avoid close proximity with infected people (as in the grocery store, airplanes, etc.) It is much safer to simply avoid contact, but when that is not possible an N95 mask will afford some measure of protection.



Will an N95 mask "protect" you? Not fully, and there are surer methods of protection. However, at less than a dollar, an N95 mask is an inexpensive, appropriate layer of protection in some circumstances.
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kestrel91316 Donating Member (1000+ posts) Send PM | Profile | Ignore Sat May-02-09 02:13 PM
Response to Original message
1. The "close proximity" CDC recommends N95 protection for is NOT
when you go to the grocery. It is intended for those must get within about 3 feet of people sick with the flu in the workplace, such as hospitals, medical offices, nursing homes, etc. CDC does NOT recommend N95 protection for the general public just going about its business in areas that do not have confirmed cases (most parts of the US - like here in Los Angeles County).

IMHO wearing any sort of mask in public places right now is just plain silly (if you are NOT sick). If you ARE sick with something like flu, you should STAY HOME. So sayeth CDC. Obviously if a sick person has to go out, any sort of mask, not just N95, will help enforce respiratory etiquette.

Straight from the horse's mouth - Interim Recommendations for Facemask and Respirator Use in Certain Community Settings Where H1N1 Influenza Virus Transmission Has Been Detected:

http://www.cdc.gov/h1n1flu/masks.htm
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hedgehog Donating Member (1000+ posts) Send PM | Profile | Ignore Sat May-02-09 02:15 PM
Response to Reply #1
2. If the flu starts spreading later on, on buses and subways, maybe?
Crowded shopping malls? Sporting events?
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kestrel91316 Donating Member (1000+ posts) Send PM | Profile | Ignore Sat May-02-09 02:19 PM
Response to Reply #2
3. AND if longer-term numbers show it to in fact be MORE dangerous
than our seasonal flus. But not now.

We don't take these steps now for season flu with its up to 1% mortality (though perhaps we should start). 35k+ people die in the US (and up to half a million worldwide) EVERY YEAR of seasonal flu and nobody gives a damn.
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MercutioATC Donating Member (1000+ posts) Send PM | Profile | Ignore Sat May-02-09 02:27 PM
Response to Reply #3
5. I agree that they may not be necessary in most circumstances.
That's not my contention.

My issue is with people who claim that they don't do anything. They do.

They're not 100% protection and they might be unnecessary in many situations, but N95 masks DO provide a layer of protection.
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kestrel91316 Donating Member (1000+ posts) Send PM | Profile | Ignore Sat May-02-09 03:28 PM
Response to Reply #5
10. We are definitely in complete agreement about that. Viral particle size
Edited on Sat May-02-09 03:28 PM by kestrel91316
isn't even a consideration to me, personally. It's the snot/spittle particles that need stopping, and they are relatively huge.
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MercutioATC Donating Member (1000+ posts) Send PM | Profile | Ignore Sat May-02-09 02:24 PM
Response to Reply #1
4. That's a lot more narrowly defined than the CDC's actual statement.
"When it is absolutely necessary to enter a crowded setting or to have close contact3 with persons who might be ill, the time spent in that setting should be as short as possible. If used correctly, facemasks and respirators may help reduce the risk of getting influenza, but they should be used along with other preventive measures, such as avoiding close contact and maintaining good hand hygiene."

http://www.cdc.gov/h1n1flu/masks.htm


Yes, close contact is defined as about three feet, but the very recommendation you cite says "crowded setting or...close contact with persons who might be ill".


I'm not suggesting that everybody should run around with masks. I am stating that, contrary to some statements made here, the use of N95 masks does provide a layer of protection.
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luvspeas Donating Member (1000+ posts) Send PM | Profile | Ignore Sat May-02-09 02:54 PM
Response to Reply #4
6. you have some very serious problems...
needing to be right at all costs does not make it so.
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uppityperson Donating Member (1000+ posts) Send PM | Profile | Ignore Sat May-02-09 03:27 PM
Response to Reply #6
9. The irony is cutting. nt
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MercutioATC Donating Member (1000+ posts) Send PM | Profile | Ignore Sat May-02-09 04:08 PM
Response to Reply #6
12. So refute the OP.
Or don't.

I know there are some here who can't logically discuss the scientific facts, but love to make silly statements like "masks don't help healthy people" and "alcohol doesn't kill viruses" despite proof to the contrary.

I can live with that.
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dipsydoodle Donating Member (1000+ posts) Send PM | Profile | Ignore Sat May-02-09 02:55 PM
Response to Reply #1
7. such as hospitals...............
use them as intended i.e wear and then hygenically dispose off. Not - wear and wear and wear ........which is what the general publoic would most likely do in the interest of economy.
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BlooInBloo Donating Member (1000+ posts) Send PM | Profile | Ignore Sat May-02-09 02:58 PM
Response to Original message
8. Alternative: live your life.
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MercutioATC Donating Member (1000+ posts) Send PM | Profile | Ignore Sat May-02-09 04:10 PM
Response to Reply #8
13. What about wearing a mask if necessary prevents one from living their life?
Spend $15-$20 for 30 masks (or more, if you want a better fit), stick 'em in a drawer, and pull 'em out and wear 'em if they're needed.

It hasn't prevented me from doing anything I normally do.
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BlooInBloo Donating Member (1000+ posts) Send PM | Profile | Ignore Sat May-02-09 04:13 PM
Response to Reply #13
14. "It hasn't prevented me from doing anything I normally do." - Do you normally wear a mask?
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MercutioATC Donating Member (1000+ posts) Send PM | Profile | Ignore Sat May-02-09 04:15 PM
Response to Reply #14
16. No, and I'm not wearing one now.
I will if the situation warrants it, though...and a situation warranting wearing a mask would also warrant other temporary lifestyle changes.

Buying masks now isn't preventing me from doing anything I normally do and wearing a mask if necessary won't prevent me from doing the things I would normally do in that situation.
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uppityperson Donating Member (1000+ posts) Send PM | Profile | Ignore Sat May-02-09 03:29 PM
Response to Original message
11. How long to they work for? If you wear one for a while, do they lose
capability to protect you? Remembering something about surgical masks being good for 15 min, but that was yrs back.

Thanks
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MercutioATC Donating Member (1000+ posts) Send PM | Profile | Ignore Sat May-02-09 04:13 PM
Response to Reply #11
15. The most stringent recommendation is to use them only once.
If they do become contaminated, they're contaminated and shouldn't be worn again.
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