RescueRanger
PDF THINK TANK: CONSULTANT
- Joined
- Sep 20, 2008
- Messages
- 16,370
- Reaction score
- 244
- Country
- Location
There are many posts on social media and misinformation / confusing and contradictory advice by both people in official and unofficial capacities regarding face masks during the coronavirus outbreak.
And as I write this I am well aware that the World Health Organisation is reviewing data from China, South Korea and Hong Kong that suggests the general public should wear face-masks and that by doing so could help contain the pandemic. [1]
This practice of spreading misinformation or misleading claims that certain masks help protect against coronavirus has created a vacuum in the supply available in the market for those who need it most and the rising demand for these items has resulted in sky rocketing prices by unscrupulous vendors looking to make a quick penny in a time of crisis.
In this write up I hope to explain how the virus is transmitted and summarise scientific evidence in support of or against each of the available masks in the Pakistani Market. Before I begin with the meat of the article, let me lay down it's bones and discuss the difference between what constitutes a face mask and what constitutes a respirator:
Paper Mask / Surgical Mask:
Within the N95 range of masks, 3M makes a very specific mask called the 3M N95 1860S (S = Surgical) this mask is solely designed for the health care sector and is the mask that is needed in hospitals at the moment but due to hoarding and increased demand is not available.
When worn correctly, these respirators are effective at filtering out the small respirable particles found in wildfire smoke. However, they do not filter out fumes and gases; for that, see the next type of respirator listed.
Half-face or full-face respirator:
Figure 1: Droplet larger than aerosols, when exhaled (at velocity of <1m/s), evaporate or fall to the ground less than 1.5 m away. When expelled at high velocity through coughing or sneezing, especially larger droplets (> 0.1 mm), can be carried by the jet more than 2m or 6m, respectively, away.[5]
What the above graph shows is that when someone coughs or sneezes they disperse a gas spray / aerosol that initially cluster near the person, being next to someone when they sneeze or cough will mean you will be exposed to the aerosol spray and larger particles given your proximity (distance) from the person coughing or sneezing.
As further time passes the larger particles settle from the air and the chance of exposure is limited. The best way to explain this is to use the diagram below:
Figure 2: In the above figure you can see that Person B will breath in both the larger and smaller particles whereas because person C is further way, whilst s/he will still inhale the particles these will be finer and smaller in concentration and this is why social distancing is so important. Source: Absolute Science Illustration
Now that we understand the basics of the transmission, we will explore the available PPE options and I will hopefully set my stall argue against mass public use of expensive masks.
1. Home made cloth masks:
A randomised trial comparing the effect of medical and cloth masks on healthcare worker illness found that those wearing cloth masks were 13 times more likely to experience influenza-like illness than those wearing medical masks.6
2. Surgical paper mask:
Several randomised trials have not found any statistical difference in the efficacy of surgical masks versus N95 FFRs at lowering infectious respiratory disease outcomes for healthcare workers.[7] However it should be noted that both the CDC and the WHO guidelines recommend N95 or FFP3 rated respirators for doctors and health care professionals working in a setting where there are procedures that would involve aerosol generating particles, procedures including swabbing, intubation/extubation, suction and ventilation.
3. N95 / P100 Masks:
A study found that health care workers risk of SARS (severe acute respiratory syndrome, also caused by a coronavirus) was lower with consistent use of N95 FFRs than with consistent use of a surgical mask.[8]
So does this mean that surgical masks are useless? Not quite, surgical masks still provide a barrier and are excellent for use by people who may be showing symptoms and people caring for people who may have symptoms.
Does this also mean that you should go out and buy N95 or FFP3 respirators to protect yourself? No, I want to make this clear that using a FFP3 respirator is pointless unless it is fit-tested and used by trained personnel, an N95 respirator or any FFP3 rated respirator should not be seen as a silver bullet and unless you are working with patients in a "hot" ward, you should please reserve these items for health care professionals who need it most.
For N95 and FFP3 masks to offer the correct protection, they have to be put on in the correct fashion and fit-tested by the user and using a "qualitative fit test":
Speaking to a friend who is a leading supplier of PPE, there is a global shortage of respirators and this is where you need to play your part and be sensible in your purchasing, do not bulk buy or hoard masks and ppe, even if it's face masks, leave some for others, if people bulk buy, it will lead to a shortage and with rising demand, business owners will hike up the prices and the poor will suffer.
It is important to mention that leading experts in their field such as Dr. Brosseau in the U.S. still advocates for the general public "not to wear masks". In comparison, in Germany The Robert Koch Institute has updated its position regarding people wearing protective face masks in public places, saying more widespread use could help slow the coronavirus spread.
To conclude, this was a non exhaustive desktop study on the transmission of COVID19 and the efficacy of the PPE available, I am in no position to predict if the WHO will change its existing position of everyone wearing masks, the data from China and elsewhere does support the general opinion that wearing masks coupled with physical distancing, staying at home and practising good hygiene can flatten the curve.
Source: Prof. Sui Huang.
[1] Devlin H, Campbell D. WHO considers changing guidance on wearing face masks. Guardian Newspaper UK 2020 Apr 1. https://www.theguardian.com/world/2...patients-should-wear-masks-says-doctors-group
[2] Gralton J, Tovey E, McLaws ML, et al. The role of particle size in aerosolised pathogen transmission: a review. J Infect 2011 Jan;62(1):1-13
[3] Yang S, Lee GWM, Chen CM, et al. The size and concentration of droplets generated by coughing in human subjects. J Aerosol Med 2007 winter;20(4):484-94
[4] Yan J, Grantham M, Pantelic J, et al. Infectious virus in exhaled breath of symptomatic seasonal influenza cases from a college community. Proc Natl Acad Sci USA 2018 Jan
[5] Van Doremalen N, Bushmaker T, Morris D, et al. Aerosol and surface stability of HCoV-19 (SARS-CoV-2) compared to SARS-CoV-1. medRxiv 2020 Mar 13
[6] MacIntyre CR, Seale H, Dung TC, et al. A cluster randomised trial of cloth masks compared with medical masks in healthcare workers.BMJ Open 2015 Apr 22;5(4):e006577
[7] Loeb M, Dafoe N, Mahony J, et al. Surgical mask vs N95 respirator for preventing influenza among healthcare workers: a randomized trial. JAMA 2009 Nov 4;302(17):1865-71
[8] Loeb M, McGeer A, Henry B, et al. SARS among critical care nurses, Toronto.Emerg Infect Dis 2004 Feb;10(2):251-5
@Foxtrot Alpha @WebMaster as requested, thread created.
And as I write this I am well aware that the World Health Organisation is reviewing data from China, South Korea and Hong Kong that suggests the general public should wear face-masks and that by doing so could help contain the pandemic. [1]
This practice of spreading misinformation or misleading claims that certain masks help protect against coronavirus has created a vacuum in the supply available in the market for those who need it most and the rising demand for these items has resulted in sky rocketing prices by unscrupulous vendors looking to make a quick penny in a time of crisis.
In this write up I hope to explain how the virus is transmitted and summarise scientific evidence in support of or against each of the available masks in the Pakistani Market. Before I begin with the meat of the article, let me lay down it's bones and discuss the difference between what constitutes a face mask and what constitutes a respirator:
Paper Mask / Surgical Mask:
- Paper dust masks: Also called surgical masks, these loose-fitting masks have only one strap and don’t form a tight seal to the wearer’s face. They are designed to stop liquid droplets and aerosols coming out of the wearer’s mouth, not filter the air coming in. With no filter and no facial seal, they are not designed to prevent the inhalation of respirable particles found in smoke. Although they may look the same, dust masks are not respirators and should not be used for that purpose.
- N95s and P100s: These respirators have two sets of straps and form a tight seal to the face. The entire respirator is made of filtering material. N95s are the most common, with P100s being more protective (similar to a HEPA filter). Both types can often be found in hardware stores and other retail outlets. These respirators are certified by the National Institute for Occupational Safety and Health (NIOSH), so look for “NIOSH” and the designation “N95” or “P100” on the respirator.
Within the N95 range of masks, 3M makes a very specific mask called the 3M N95 1860S (S = Surgical) this mask is solely designed for the health care sector and is the mask that is needed in hospitals at the moment but due to hoarding and increased demand is not available.
When worn correctly, these respirators are effective at filtering out the small respirable particles found in wildfire smoke. However, they do not filter out fumes and gases; for that, see the next type of respirator listed.
Half-face or full-face respirator:
- Half-face or full-face respirator: Unlike N95s and P100s, which are disposable, half-face and full-face respirators offer a tight-fitting, flexible facepiece with replaceable filter cartridges. N95 particulate filters or purple (P100 or HEPA) filter cartridges will protect against particulates in wildfire smoke. When used with a combination filter that has an organic vapor cartridge, these respirators would also protect against harmful fumes and gases. However, neither these respirators nor N95s supply oxygen.
Figure 1: Droplet larger than aerosols, when exhaled (at velocity of <1m/s), evaporate or fall to the ground less than 1.5 m away. When expelled at high velocity through coughing or sneezing, especially larger droplets (> 0.1 mm), can be carried by the jet more than 2m or 6m, respectively, away.[5]
What the above graph shows is that when someone coughs or sneezes they disperse a gas spray / aerosol that initially cluster near the person, being next to someone when they sneeze or cough will mean you will be exposed to the aerosol spray and larger particles given your proximity (distance) from the person coughing or sneezing.
As further time passes the larger particles settle from the air and the chance of exposure is limited. The best way to explain this is to use the diagram below:
Figure 2: In the above figure you can see that Person B will breath in both the larger and smaller particles whereas because person C is further way, whilst s/he will still inhale the particles these will be finer and smaller in concentration and this is why social distancing is so important. Source: Absolute Science Illustration
Now that we understand the basics of the transmission, we will explore the available PPE options and I will hopefully set my stall argue against mass public use of expensive masks.
1. Home made cloth masks:
A randomised trial comparing the effect of medical and cloth masks on healthcare worker illness found that those wearing cloth masks were 13 times more likely to experience influenza-like illness than those wearing medical masks.6
2. Surgical paper mask:
Several randomised trials have not found any statistical difference in the efficacy of surgical masks versus N95 FFRs at lowering infectious respiratory disease outcomes for healthcare workers.[7] However it should be noted that both the CDC and the WHO guidelines recommend N95 or FFP3 rated respirators for doctors and health care professionals working in a setting where there are procedures that would involve aerosol generating particles, procedures including swabbing, intubation/extubation, suction and ventilation.
3. N95 / P100 Masks:
A study found that health care workers risk of SARS (severe acute respiratory syndrome, also caused by a coronavirus) was lower with consistent use of N95 FFRs than with consistent use of a surgical mask.[8]
So does this mean that surgical masks are useless? Not quite, surgical masks still provide a barrier and are excellent for use by people who may be showing symptoms and people caring for people who may have symptoms.
Does this also mean that you should go out and buy N95 or FFP3 respirators to protect yourself? No, I want to make this clear that using a FFP3 respirator is pointless unless it is fit-tested and used by trained personnel, an N95 respirator or any FFP3 rated respirator should not be seen as a silver bullet and unless you are working with patients in a "hot" ward, you should please reserve these items for health care professionals who need it most.
For N95 and FFP3 masks to offer the correct protection, they have to be put on in the correct fashion and fit-tested by the user and using a "qualitative fit test":
Speaking to a friend who is a leading supplier of PPE, there is a global shortage of respirators and this is where you need to play your part and be sensible in your purchasing, do not bulk buy or hoard masks and ppe, even if it's face masks, leave some for others, if people bulk buy, it will lead to a shortage and with rising demand, business owners will hike up the prices and the poor will suffer.
It is important to mention that leading experts in their field such as Dr. Brosseau in the U.S. still advocates for the general public "not to wear masks". In comparison, in Germany The Robert Koch Institute has updated its position regarding people wearing protective face masks in public places, saying more widespread use could help slow the coronavirus spread.
To conclude, this was a non exhaustive desktop study on the transmission of COVID19 and the efficacy of the PPE available, I am in no position to predict if the WHO will change its existing position of everyone wearing masks, the data from China and elsewhere does support the general opinion that wearing masks coupled with physical distancing, staying at home and practising good hygiene can flatten the curve.
Source: Prof. Sui Huang.
[1] Devlin H, Campbell D. WHO considers changing guidance on wearing face masks. Guardian Newspaper UK 2020 Apr 1. https://www.theguardian.com/world/2...patients-should-wear-masks-says-doctors-group
[2] Gralton J, Tovey E, McLaws ML, et al. The role of particle size in aerosolised pathogen transmission: a review. J Infect 2011 Jan;62(1):1-13
[3] Yang S, Lee GWM, Chen CM, et al. The size and concentration of droplets generated by coughing in human subjects. J Aerosol Med 2007 winter;20(4):484-94
[4] Yan J, Grantham M, Pantelic J, et al. Infectious virus in exhaled breath of symptomatic seasonal influenza cases from a college community. Proc Natl Acad Sci USA 2018 Jan
[5] Van Doremalen N, Bushmaker T, Morris D, et al. Aerosol and surface stability of HCoV-19 (SARS-CoV-2) compared to SARS-CoV-1. medRxiv 2020 Mar 13
[6] MacIntyre CR, Seale H, Dung TC, et al. A cluster randomised trial of cloth masks compared with medical masks in healthcare workers.BMJ Open 2015 Apr 22;5(4):e006577
[7] Loeb M, Dafoe N, Mahony J, et al. Surgical mask vs N95 respirator for preventing influenza among healthcare workers: a randomized trial. JAMA 2009 Nov 4;302(17):1865-71
[8] Loeb M, McGeer A, Henry B, et al. SARS among critical care nurses, Toronto.Emerg Infect Dis 2004 Feb;10(2):251-5
@Foxtrot Alpha @WebMaster as requested, thread created.
Last edited:
