Are these respirators spewing covid viruses?

[chirhone]

Where are you?

Philippines. Our lockdown started in March 16, the president extended it to May 15, but hinted he would only lift it if there is vaccine already. I'm stuck at house and no confidence to even go out to drugstore or clinic so I need to use more protection like the full face respirator. So I want to know exactly it compares to the surgical mask in exhalation dynamics (so I can defend its use with reasonings for people who may point out there is exhalation valve present).

 

[berkeman]

Initially i didn't want to get it because people may complain there is no filter in the exhalation valve. But then since surgical mask and N95 also allows exhalation outside it. Then they are similar.

No. Respirators generally do not filter exhalations ("expirations") by the person wearing them. That's not what they are for. The are for protecting the person wearing them. A traditional N95 filter mask that is well-fitting will filter both inspirations and expirations by the wearer, protecting both the person wearing the mask and the patient they are treating. That assumes a very good fit that still works well on expiration (when the mask will tend to lift off of your face a bit if it is not tight and well-fitting).

In an EMS meeting that I was in today, an MD called out a picture of a medic wearing an "N95" mask that had a visible valve on it. He emphasized that such masks with valves like that have a 1-way expiration valve, which exposes your patient to your breath if you are pre-symptomatic for COVID-19.

https://www.zoro.com/static/cms/product/large/Z-519yfo9x4.JPG

This is why I want to know how exactly the surgical mask behave so I can justify using it. Also because N95 are getting so expensive and scarce the public no longer use it. What do you think will allow more exhalation out, the full face respirator above or a typical surgical mask?

Surgical masks do not filter out the smallest viral particles that are shed on expiration, but do help a lot to trap the liquid droplets that contain the virus. That helps to keep you from depositing such droplets on surfaces when you cough or sneeze. That's about the extent of the use of surgical masks -- they are meant to help to keep you from spreading the virus if you are shedding it and are in a public place. They are far from perfect, but still a useful step, IMO.

 

[chirhone]

No. Respirators generally do not filter exhalations ("expirations") by the person wearing them. That's not what they are for. The are for protecting the person wearing them. A traditional N95 filter mask that is well-fitting will filter both inspirations and expirations by the wearer, protecting both the person wearing the mask and the patient they are treating. That assumes a very good fit that still works well on expiration (when the mask will tend to lift off of your face a bit).

In an EMS meeting today, an MD called out a picture of a medic wearing an "N95" mask that had a visible valve on it. He emphasized that such masks with valves like that had the 1-way expiration valve, which exposes your patient to your breath if you are pre-symptomatic for COVID-19.

https://www.zoro.com/static/cms/product/large/Z-519yfo9x4.JPG

View attachment 261365

Surgical masks do not filter out the smallest viral particles that are shed on expiration, but do help a lot to trap the liquid droplets that contain the virus. That helps to keep you from depositing such droplets on surfaces when you cough or sneeze. That's about the extent of the use of surgical masks -- they are meant to help to keep you from spreading the virus if you are shedding it and are in a public place. They are far from perfect, but still a useful step, IMO.

But can't one say the full face respirator also help trap a lot of liquid droplets that contain the virus and also not able to filter out the smallest viral particles that are shed on expiration? Just like the surgical masks?

 

[berkeman]

But can't one say the full face respirator also help trap a lot of liquid droplets that contain the virus and also not able to filter out the smallest viral particles that are shed on expiration? Just like the surgical masks?

That's probably fairly accurate, depending on whether the expiration valves have any baffles in them (which they probably don't). You can stack masks to get extra protection effects if you can tolerate it. You could wear a surgical mask under your respirator to help to protect others better, for example.

 

[berkeman]

In an EMS meeting today, an MD called out a picture of a medic wearing an "N95" mask that had a visible valve on it. He emphasized that such masks with valves like that have a 1-way expiration valve, which exposes your patient to your breath if you are pre-symptomatic for COVID-19.

BTW, the MD made a semi-humorous comment about the picture of the health provider wearing the mask with the expiration valve -- "When EMS has to go to Home Depot to purchase emergency supplies, you end up with compromises like this".

 

[chirhone]

That's probably fairly accurate, depending on whether the expiration valves have any baffles in them (which they probably don't). You can stack masks to get extra protection effects if you can tolerate it. You could wear a surgical mask under your respirator to help to protect others better, for example.

I have tried to seal the exhalation valve of the half face respirator but it becomes more difficult to exhale. I can do it partially with the breath deflected to my neck. Would this perform similar to the surgical masks? I mentioned surgical masks because n95 are now so expensive and scarce, the public no longer use them. So i need to compare the half face and full face respirators to surgical masks only, not n95.

How do you compare a surgical mask only to the half or full face respirator as far as exhalation is concerned? Which has highest score or lower score. This is the hole in the half face respirator (which is similar to the full face respirator) with a small thin rubber flap shown in my original message)

 

[berkeman]

I have tried to seal the exhalation valve of the half face respirator but it becomes more difficult to exhale. I can do it partially with the breath deflected to my neck. Would this perform similar to the surgical masks?

No. Put on your cloth surgical mask. Then put on your respirator.

How do you compare a surgical mask only to the half or full face respirator as far as exhalation is concerned?

The surgical cloth mask will do a better job of stopping respiratory droplets on expiration, coughing and sneezing.

What is your end game (apologies if you've stated it already in this thread). To protect yourself, or to also protect others?

 

[chirhone]

No. Put on your cloth surgical mask. Then put on your respirator.The surgical cloth mask will do a better job of stopping respiratory droplets on expiration, coughing and sneezing.

What is your end game (apologies if you've stated it already in this thread). To protect yourself, or to also protect others?

To protect myself and others. Just want something to protect my eyes too. The half face and full face respirators are air tight and inhalation is only via the filters so this is the plus side uncontroversial. The only concern is exhalation.

However my half face respirator has deflector downward. So the shield can take the droplets, and not direct to the front. So pls help reanalyze why a surgical mask only is still superior to it?

 

[berkeman]

Just want something to protect my eyes too.

If your respirator does not have eye protection built-in, wear goggles.

However my half face respirator has deflector downward. So the shield can take the droplets, and not direct to the front. So pls help reanalyze why a surgical mask only is still superior to it?

Wakarimasen...

 

[chirhone]

If your respirator does not have eye protection built-in, wear goggles.

Wakarimasen...

Hope phinds can share the full air flow dynamics. Also i found condensation in the shield. Pls explain the physics of why there is condensation. Medical doctors i ask can't explain the physics of it. So i need to know and explain to them. Thanks.

 

[berkeman]

Hope phinds can share the full air flow dynamics.

Please use the "@" symbol in front of any user or K9 like @phinds that you would like to flag for comment. Thank you.

Pls explain the physics of why there is condensation. Medical doctors i ask can't explain the physics of it. So i need to know and explain to them. Thanks.

What condensation? You mean like your glasses fogging up when you wear a mask?

 

[chirhone]

Please use the "@" symbol in front of any user or K9 like @phinds that you would like to flag for comment. Thank you.What condensation? You mean like your glasses fogging up when you wear a mask?

There are many drops of water in the deflector. I read phinds (or is it bill?) having the same experience where it drops to his wood.

Many in the public using these now. So let's scrutinize all this in gross details in the physics and hydro air dynamics principles.

 

[atyy]

To protect myself and others. Just want something to protect my eyes too. The half face and full face respirators are air tight and inhalation is only via the filters so this is the plus side uncontroversial. The only concern is exhalation.

However my half face respirator has deflector downward. So the shield can take the droplets, and not direct to the front. So pls help reanalyze why a surgical mask only is still superior to it?

@berkeman suggested wearing a cloth mask under your respirator if you are concerned about infecting others. Would it work to just get some cloth and tape it over the opening? That would at least catch droplets, and would be ok until it got wet (ie. like a cloth mask outside, instead of inside the respirator)?

 

[chirhone]

@berkeman suggested wearing a cloth mask under your respirator if you are concerned about infecting others. Would it work to just get some cloth and tape it over the opening? That would at least catch droplets, and would be ok until it got wet (ie. like a cloth mask outside, instead of inside the respirator)?

I can wear surgical mask over the respirator outlet. But it can deflect the breath to my neck. How does this compare to the surgical masks in deflecting the breath? I just want to justify using it. So let's analyze it in the residual breath escaped from these ppe.

The reason i can't wear surgical mask then respirator over it bec it can affect the air tightness of the nose or face shield.

 

[atyy]

I can wear surgical mask over the respirator outlet. But it can deflect the breath to my neck. How does this compare to the surgical masks in deflecting the breath? I just want to justify using it. So let's analyze it in the residual breath escaped from these ppe.

The reason i can't wear surgical mask then respirator over it bec it can affect the air tightness of the nose or face shield.

What I mean was instead of wearing a mask under your respirator, why not take some cloth and tape it over the respirator exit?

The proper analysis needed seems unavailable at the moment. The paper you posted in #28 gives evidence that neither a surgical mask nor a cloth mask will protect others from a cough at a distance of 20 cm. However, they did not exclude that the surgical or cloth mask might reduce the distance that droplets can travel. If they can do that, then the surgical or cloth mask would still protect others when combined with (1) not going out unless you feel well, ie. no symptoms, not even mild ones, so that if there is any spread it would be either presymptomatic or asymptomatic spread (2) social distancing as much as possible, avoid going out unless necessary, ie. talk to others and receive/hand them packages at 1.5 m apart (3) wash your hands before and after handling and cleaning your mask.

 

[chirhone]

What I mean was instead of wearing a mask under your respirator, why not take some cloth and tape it over the respirator exit?

I tried taping cloth over the hole at bottom but it makes it so hard to exhale. One must deflect the breath to the neck to breath easier. If so i wonder how this combination compares to the surgical mask as far as leaking breath is concerned.

The proper analysis needed seems unavailable at the moment. The paper you posted in #28 gives evidence that neither a surgical mask nor a cloth mask will protect others from a cough at a distance of 20 cm. However, they did not exclude that the surgical or cloth mask might reduce the distance that droplets can travel. If they can do that, then the surgical or cloth mask would still protect others when combined with (1) not going out unless you feel well, ie. no symptoms, not even mild ones, so that if there is any spread it would be either presymptomatic or asymptomatic spread (2) social distancing as much as possible, avoid going out unless necessary, ie. talk to others and receive/hand them packages at 1.5 m apart (3) wash your hands before and after handling and cleaning your mask.

 

[Laroxe]

People seem to be working on the principle that its possible to achieve complete protection, that's really not easy. Wearing masks is about reducing risk, for people working with people already infected a N95 mask will reduce the risks from droplets and its entirely predictable that the external surface will become contaminated. The exhaust valve makes breathing easier when they are used over long periods, as the patients are already infected and other staff are wearing similar PPE the increased risk from the valve is irrelevant.

For the general public the most effective prevention is in social distancing, despite all the alarmist claims of viruses being detectable miles away, maintaining a distance of 2 metres leads to the biggest risk reductions and is practical. The greatest risk is in enclosed spaces or where social distancing can't be maintained. As we know that people may be infectious before they become symptomatic, if someone in this incubation period wears a cloth mask, it reduces spreading potentially infected droplets and slows the velocity of exhalations. The effects of this on the spread of the virus becomes most significant in enclosed areas and where we have close contact, they may have little advantage in open spaces outdoors.

Any potential advantages may also be offset by peoples tendency to adjust and touch the mask while it is being worn, this would increase the risk to people uninfected. Really to be most effective people would need training in the use of masks, their safe removal and their cleaning. Wearing a full face respirator may make people less likely to maintain social distancing and cleaning the external surfaces, the effects of such masks when people can maintain distance and good hygiene is likely to be fairly insignificant. They have no impact on the risks from infected surfaces or people we live with.