2_About Masks by CDC

3_Considerations for Wearing Masks by CDC

4_Advice on the use of masks in the context of COVID-19

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.

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 :https://clinicaltrials.gov/ct2/show/study/NCT00173017
https://www.researchgate.net/publication/7823790_Effects_of_wearing_N95_and_surgical_facemasks_on_heart_rate_thermal_stress_and_subjective_sensations

5_Fairy Diff N95-KN95

RAYMOND J. ROBERGE1*, EMILY BAYER1, JEFFREY B. POWELL2, AITOR COCA1, MARC R. ROBERGE1 and STACEY M. BENSON2
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.

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.