Sayak Nandi
Department of Textile Technology
Government College of Engineering and Textile Technology, Serampore,WB, India
Introduction
In the current situation, when the world is facing a major pandemic without a certified cure; PPE seems to be the last resort. Mask is a part of PPE, which has become possibly the most vital part of it. So, I have tried to give a little more insight into masks also sighting some recent developments and common mistakes etc.
Reason
why mask is so essential in this pandemic
When we consider the mode of transmission by COVID-19, it is contact, droplet or airborne [1]. Hence the PPE designed should be effective in preventing these three modes as shown in Table. 1.
Mode of Transmission |
PPE to be used |
Guidelines and
advices to Prevent these modes |
Contact |
Gloves,
Apron |
Washing
hands frequently with soaps or use of at least 60% alcohol based sanitizers |
Droplet |
Gloves,
Apron, Fluid Resistant Mask, Eye Protection |
Use
of Masks and maintaining social distancing |
Airborne |
Gloves,
Fluid repellent gown, Eye Protection, Mask |
Use
of Masks and maintaining social distancing |
Hence, Masks have been the
most crucial part of PPE with very little knowledge to common people. However
we go by the initial guidelines provided by Government [3], it doesn’t
recommend the use of PPEs for common people. However certain international
research [4] claims, use of N95 masks reduces infection. Later the use of masks was made mandatory.
Mechanism of
Filtration
The filters used in modern surgical masks and respirators
are generally made from nonwovens- fibre porosity, diameter and thickness of
filter determines the efficiency of a mask. Generally there are 4 types of
filter mechanism shown in Fig. 1.
Fig. 1: Filter mechanisms [5] |
Inertial
impaction: Filtration for large particles; the large particles
diverted around a filter fibre structure due to its size.
Interception: Filtration
for large particles; the intercepted particle can be prevented by fine filter
fibres.
Diffusion: Filtration
for small particles; the small particles that are bombarded by air molecules,
causing it to deviate from air stream and come in contact with filter fibre.
Electrostatic
attraction: Filtration for oppositely charged particles;
If the charge of filter fibre is opposite to the charge of particle, it causes
attraction. This mechanism doesn’t favor any particular particle size.
More about N95 masks
and Multi layered Masks
In a PPE use of N95 masks or multilayered masks (minimum
3 layers) are recommended [6], since it provides maximum protection against
COVID-19. [5] [7].
N95 masks: The
word N signifies “Nonresistant to oil” and “95” signify
95% filtration to aerosols. The masks are generally made from fibres of
diameter 1 micron of thermoplastic like polypropylene, polyester etc. using
melt blown technique.
Respirator filters are rated as N, R or P for their level
of protection against oil and aerosols. Where “R” is little oil resistant
and “P” is strongly oil resistant. The oil removes the electrostatic charges
from the filter media, hence greater the
oil resistance greater the filtration.
Multilayered masks: Generally made from non-woven thermoplastic like polypropylene, polyester etc. using melt blown technique. The masks are generally 3-4 layered for better filtration. Even FFP2 and FFP3 masks are also recommended in certain parts. (Filtration 94% and 99% respectively).Researches regarding usage of FFP2 and FFP3 and N95 is shown, though the masks have a high filtration rate; however particle influx through face shield leakage of the N95 respirators far exceeds the influx through the filter. The ratio of face seal leakage to filter leakage is in range of 7-20:1, so it is advisable to dispose these respirators and not reusing it multiple times [8]
General mistakes by
common people
In common it is seen people using surgical masks, home-made masks and paper masks in spite of guidelines. It is known that home-made masks and paper masks cannot provide the same degree of protection. A study shows choice of material might affect the filtration, use of silk shows higher filtration (approx. 90%) than coarse cotton (70%)[9].This might be due to silk forms strong electrostatic charges and enhances filtration.
Even in a study shows protection factor of surgical mask against particle 0.04-1.3 μm was on average of 8 to 12 times less than N95 masks [10]. Another study also suggests surgical mask filters ranges from 10% to nearly 90% [5]. Hence N95 respirator and multilayered masks must be used for better protection. A better difference for surgical mask, paper mask and N95 mask is provided in Fig. 2.
Fig. 2: Difference between
surgical mask, paper mask and N95 mask [11]
Some extra
information about Masks
Researches have also been conducted to achieve reusable
N95 masks with flexible nonporous Si-based replaceable membrane to enhance
filtration efficiency [12].
Certain researches involves the comfort perspective of
the masks, the use of atraumatic silicon border dressing to prevent skin
injuries due to use of tight masks for long hours was carried out for the front
line warriors [13].
Recent Trends and
Conclusion
Certain companies have
recently been manufacturing reusable masks with antimicrobial finishing. These
masks retains its anti-microbial efficacy upto certain washing cycles, these
masks are highly recommended and might be a useful weapon in this situation. However
certain fashionable masks that don’t provide adequate safety are also available
in market. So it is advisable to buy and use masks that are effective, rather
than only fashionable ones. Since masks and PPEs might be our “Last Resort” in
this pandemic till any proper medication is available.
References:
- Cook, T.M. (2020). Personal protective equipment during the Covid-19 pandemic-a narrative review. Anaesthesia, 75(7), 920-923. https://doi.org/10.1111/anae.15071
- WHO. (2020, May 5). WHO SAVE LIVES: CLEAN YOUR HANDS IN THE CONTEXT OF COVID-19. https://www.who.int/infection-prevention/campaigns/clean-hands/en/
- Ministry of Health and Family Welfare. (2020). Novel Coronavirus Disease 2019 (COVID-19): Guidelines on rational use of Personal Protective Equipment. Indian Ministry of Health and Family Welfare Directorate General of Health Services. https://www.mohfw.gov.in/pdf/GuidelinesonrationaluseofPersonalProtectiveEquipment.pdf&ved=2ahUKEwjtvYTQtqbqAhX-xTgGHez8DekQFjABegQIChAG&usg=AOvVaw3EdMY_uB2dz11E5Kxfgi8r&cshid=1593413208055
- Law, S.K., Leung, A.W.N., & Xu, C. (2020). Are face mask useful for limiting the spread of COVID-19?. Hong Kong Medical Journal, 26, 267-268. https://doi.org/10.12809/hkmj208566
- Brosseau, L., Ann, R.B. (2009, October 14). N95 Respirators and Surgical Masks. NIOSH Science Blog, Centers for Disease Control and Prevention. https://blogs.cdc.gov/niosh-science-blog/2009/10/14/n95/
- The Times of India. (2020, April 20). GOING INTO THE COVID FIGHT WITH HOLES IN THEIR SHIELD [Press release]. https://m.timesofindia.com/india/going-into-the-covid-fight-with-holes-in-their-shields/articleshow/75246825.cms
- Henneberry, B. (2020). How to make Personal Protective Equipment (PPE) for COVID-19 (Manufacturing and Sourcing Guide). Thomasnet. https://www.thomasnet.com/articles/plant-facility-equipment/how-to-make-ppe/
- Faris, C., Deben, K., van Haesendonck. G, et al. Making sense of personal protective equipment PPE and tracheostomy in the mists of the 2020 COVID-19 crisis. B-ENT 2 May 2020. https://doi.org/10.5152/B-ENT.2020.20128
- Strong-Wright, J. (2020). A Brief Review of Materials and Designs for Homemade Masks to Protect Against COVID-19. Preprints, 1-11. https://doi.org/10.20944/preprints202006.0132.v1
- Lee, S. A., Grinshpun, S. A. & Reponen, T. (2008). Respiratory performance offered by N95 respirators and surgical masks: human subject evaluation with NaCl aerosol representing bacterial and viral particle size range. The Annals of Occupational Hygiene, 52: 177-185. https://doi.org/10.1093/annhyg/men005
- Laborer’s Health & safety fund of North America. (2020). How Effective are Masks and Other Facial Coverings at stopping Coronavirus. https://www.lhsfna.org/index.cfm/lifelines/may-2020/how-effective-are-masks-and-other-facial-coverings-at-stopping-coronavirus/
- El-Atab, N., Qaiser, N., Badghaish, H.S., Shaikh, S.F. & Hussain, M.M. (2020). A Flexible Nanoporous Template for Design and Development of Reusable Anti-COVID-19 Hydrophobic Face Masks. ACS Nano., 1-22. https://doi.org/10.1021/acsnano.0c03976
- Smart, H., Opinion, F.B., Darwich, I., Elnawasany, M.A., & Kodange, C. (2020). Preventing Facial Pressure Injury for Health Care Providers Adhering to COVID-19 Personal Protective Equipment Requirements. Advances in Skin & wound care, 33, 1-9. https://doi.org/10.1097/01.ASW.0000669920.94084.c1
3 Comments
Very informative and useful article. Thanks to the author .
ReplyDeleteNice one....too much informative
ReplyDeleteUseful and very much relevant in the present context
ReplyDelete