Knowledge Center

1. About COVID-19 Virus by Centres for Disease Control & Prevention(CDC)
2. About Masks by Centres for Disease Control & Prevention (CDC)
3. Considerations for wearing masks byCentres for Disease Control & Prevention(CDC)
4. WHO Advice on the use of masks in the context of COVID-19
5. Dos and Donts of Using a Face Mask

6. What are the effects of wearing a N95 Mask ?
The use of N95 masks increases effort in breathing. For some people, the use of N95 mask may cause discomfort in breathing, tiredness or headache. This may be due to the mask causing increased resistance to breathing, and a reduction in the volume of air breathed. For most people this is not serious.
However, some elderly people, people with lung or heart conditions, and women in the later stages of pregnancy may already have reduced lung volumes or breathing issues.
You should take a break from using a N95 mask if you feel uncomfortable. Elderly, pregnant women and people with severe lung or heart problems who have difficulty breathing at rest or on exertion should consult their doctor as to whether they should use the N95 mask.
Women in the 2nd and 3rd trimesters of pregnancy may already have reduced lung volumes or breathing issues. They should stop using a N95 mask if they feel uncomfortable.
7. Effects of wearing N95 and surgical facemasks on heart rate, thermal stress and subjective sensations

The study was aimed at investigating the effects of wearing N95 and surgical facemasks with and without nano-functional treatments on thermophysiological responses and the subjective perception of discomfort. Five healthy male and five healthy female participants performed intermittent exercise on a treadmill while wearing the protective facemasks in a climate chamber controlled at an air temperature of 25 degrees C and a relative humidity of 70%. Four types of facemasks, including N95 (3M 8210) and surgical facemasks, which were treated with nano-functional materials, were used in the study.
(1) The subjects had significantly lower average heart rates when wearing nano-treated and untreated surgical facemasks than when wearing nano-treated and untreated N95 facemasks.
(2) The outer surface temperature of both surgical facemasks was significantly higher than that of both N95 facemasks. On the other hand, the microclimate and skin temperatures inside the facemask were significantly lower than those in both N95 facemasks.
(3) Both surgical facemasks had significantly higher absolute humidity outside the surface than both N95 facemasks. The absolute humidity inside the surgical facemask was significantly lower than that inside both N95 facemasks.
(4) Both surgical facemasks were rated significantly lower for perception of humidity, heat, breath resistance and overall discomfort than both N95 facemasks. The ratings for other sensations, including feeling unfit, tight, itchy, fatigued, odorous and salty, that were obtained while the subjects were wearing the surgical facemasks were significantly lower than when the subjects were wearing the N95 facemasks.
(5) Subjective preference for the nano-treated surgical facemasks was the highest. There was significant differences in preference between the nano-treated and untreated surgical facemasks and between the surgical and N95 facemasks. We discuss how N95 and surgical facemasks induce significantly different temperature and humidity in the microclimates of the facemasks, which have profound influences on heart rate and thermal stress and subjective perception of discomfort.

Source :

8. Evaluation of N95 Respirator- Effects on Breathing Resistance & Inhaled Carbon Dioxide
Published by Oxford University Presson behalf of the British Occupational Hygiene Society 2012
Ann. Occup. Hyg., Vol. 57, No. 3, pp. 384–398, 2013

Objective: For pandemic influenza outbreaks, the Institute of Medicine has recommended using asurgical mask cover (SM) over N95 filtering facepiece respirators(FFRs) among healthcare workers as one strategy to avoid surface contamination of theFFR which would extend its efficacy and reduce the threat of exhausting FFR supplies.The objective of this investigation was to measure breathing airquality and breathingresistance when using FFRs with US Food and Drug Administration-cleared SM and
without SM.
Methods: Thirty National Institute for Occupational Safety and Health (NIOSH)-approved
FFR models with and without SM were evaluated using the NIOSH Automated Breathing andMetabolic Simulator (ABMS) through six incremental work rates.
Results: Generally, concentrations of average inhaled CO2 decreased and average inhaledO2 increased with increasing O2 consumption for FFR+SM and FFR-only. For most workrates, peak inhalation and exhalation pressures were statistically higher in FFR+SM ascompared with FFR-only. The type of FFR and the presence of exhalation valves (EVs) hadsignificant effects on average inhaled CO2, average inhaled O2, and breathing pressures.The evidence suggests that placement of an SM on one type of FFR improved inhaledbreathing gas concentrations over the FFR without SM; the placement of an SM overan FFR+EV probably will prevent the EV from opening, regardless of activity intensity;and, at lower levels of energy expenditure, EVs in FFR do not open either with or withoutan SM.
Conclusions: The differences in inhaled gas concentrations in FFR+SM and FFR-onlywere significant, especially at lower levels of energy expenditure. The orientation of theSM on the FFR may have asignificant effect on the inhaled breathing quality andbreathing resistance, although the measurable inhalation and exhalation pressurescaused by SM over FFR for healthcare users probably will be imperceptible at loweractivity levels.

9. Difference between N95 and KN95
10. Effect of Exhaled Moisture on Breathing Resistance of N95 Filtering Facepiece RespiratorsFacepiece Respirators
National Institute for Occupational Safety and Health, National Personal Protective Technology
Laboratory, Pittsburgh, PA 15236, USA; 2Technology Research Branch, EG & G Technical Services,
Pittsburgh, PA 15236, USA

This study evaluated the effect of exhaled moisture on the breathing resistance of three classesof filtering facepiece respirators (FFR) following 4 h of continuous wear at a breathing volumeof 40 l min21, utilizing an automated breathing and metabolic simulator as a human surrogate.After 4 h, inhalation and exhalation resistance increased by 0.43 and 0.23 mm of H2O pressure,respectively, and average moisture retention in the respirators was 0.26 ml. Under ambientconditions similar to those of the current study, and at similar breathing volumes, it is unlikelythat exhaled moisture will add significantly to the breathing resistance of filtering facepiecerespirators (FFR) over 4 h of use.
Moisture exhaled over 4 h from an ABMS througha breathing mannequin fitted with NIOSH-certifiedN95 FFR, SN95 FFR, and N95 FFR/EV, at a moderate breathing volume and mean ambient conditionsof 20.40C temperature (range, 18.10–21.50C)and relative humidity 51.76% (range, 40.00–63.5%), did not accumulate to any significant degreewithin the FFR. A minor increase (3%) in inhalationand exhalation resistances occurred concurrentlythat would likely be imperceptible to the wearer. Exhaled moisturedoes not significantly impact the mechanics of breathing resistance while wearing N95FFR, SN95 FFR, and N95 FFR/EV over 4 h at moderate breathing volumes.

11. Repeated coughing adversely affects filtering capability
Source : The Economic Times –Panache 22.07.20
LONDON: While facial masks reduce the spread of COVID-19, their filtering efficiency is adversely affected by repeated coughing, according to a new study which recommends complete personal protective equipment for healthcare workers including helmets with built-in air filters, and face shields.

Scientists, including TalibDbouk and Dimitris Drikakis from the University of Nicosia in Cyprus, used computer models to map out the expected flow patterns of small droplets released when mask-wearing person coughs repeatedly.

Earlier computer simulations the researchers showed that droplets of saliva can travel 18 feet in five seconds when an unmasked person coughs.
In the current study, published in the journal Physics of Fluids, they used an extended model to consider the effect of multiple cycles of coughing on the filtering efficiency of face masks.
According to the study, while masks can reduce the spread of airborne droplets, their effectiveness is adversely affected by repeated coughing, as might happen when an individual is ill.
The scientists added that the use of a mask does not provide complete protection, and social distancing remains important during a pandemic.
In the analysis, the researchers modelled a sequence of coughs by applying several cycles of forward-directed velocity pulses to the initial droplets.
They then performed numerical simulations to account for droplet interactions with the porous filter in a surgical mask.
According to the scientists, even when a mask is worn, some droplets can travel a considerable distance, up to one metre, during bouts of mild coughing.Without a mask, they said droplets travel twice as far, adding that wearing a mask will help.While masks also decrease the number of droplets leaking out the sides of the mouth, they fail to eliminate this entirely, the researchers said. “The droplet sizes change and fluctuate continuously during cough cycles as a result of several interactions with the mask and face,” said Drikakis.

“Masks decrease the droplet accumulation during repeated cough cycles. However, it remains unclear whether large droplets or small ones are more infectious,” Dbouk explained.
Based on the results, the researchers recommended much more complete personal protective equipment for healthcare workers, including helmets with built-in air filters, face shields, disposable gowns, and double sets of gloves.They also urged manufacturers and regulatory authorities to consider new criteria for assessing mask performance which account for flow physics and cough dynamics.

12. Effects of long-duration wearing of N95 respirator and surgical facemask

a pilot study-Journal of Lung, Pulmonary & Respiratory Research,

Volume 1 Issue 4 – 2014, Jian Hua Zhu,ShuJin Lee, De Yun Wang,HeowPueh Lee

The protection efficacy of facemasks and respirators has been well documented. Thechange of human nasal functions after wearing N95 respirator and surgical facemask isnot known. In a parallel group study,we recruited 87 healthy healthcare workers. Eachof the volunteers attended two sessions, and wore N95 respirator in session 1 (S1)and surgical facemask in session 2 (S2) for 3hours. Mean minimum cross sectionalarea (mMCA) of the two nasal airways via acoustic rhinometry and nasal resistancevia rhinomanometry were measured before and immediately after the mask wearing.Rhinomanometry wasrepeated every 30minutes for 1.5hours after the removal ofmasks. A questionnaire was distributed toeach of the volunteers, during the 3hoursmask wearing period, to report subjective feelings on discomfort level of breathingactivity. Among 77 volunteers who completed both the two sessions, the mean nasalresistance immediately increased upon the removal of surgical facemask and N95respirator. The mean nasal resistance was significantly higher in S1 than S2 at 0.5 hourand 1.5hours after removal of the masks (p<0.01). There is no statistical difference onmMCA before and after mask wearing in both sessions (p=0.85). The discomfort levelwas increasing with time while wearing masks, with significantly higher magnitude inS1 (p<0.001). There is an increase of nasal resistance upon removal of N95 respiratorand surgical facemask potentially due to nasal physiological changes. N95 respiratorcaused higher post-wearing nasal resistance than surgical facemask with differentrecovering routines.

In  conclusion,  there  is  an  increase  of  nasal  resistance  uponremoval of N95 respirator and surgical facemask after 3hours wearingwhich potentially due to nasal physiological changes, instead of thesize  of nasal airways. Thenasal resistance was not recovered even after 1.5hours removal ofrespirator/facemask. In addition, the N95 respirator caused higher post-wearing nasal resistance than surgical facemask with different recovery routines. This pilot study has certain limitations. Firstly, the number of volunteers recruited was not largeenough to eliminate the magnitude difference of mean nasal resistances at  the  beginning  of  sessions  1  and  2,  though  statistically  the  nullhypothesis is acceptable. Secondly, the time monitored after removal of respirator/facemask, 1.5hours, was not long enough for the nasal resistance recovering to the baseline level, which is of importance. The limitation in the study time interval is due to the requirement thatthe volunteers are to remain in the study centre without consumptionof foods and therefore we could not keep the volunteers for too long. Thirdly, the effects of nasal cycle could not be ruled out in monitoringthe nasal resistance change before and after mask wearing based upon the current test settings.