National Library of Medicine (Collection of studies)
Each of these are from NLM.
“The face seal leakage was manifested as decreased efficiency for large particles and also for total mass, while the particles in the micrometer range contained the major part of the test aerosol mass. The particle number efficiency diagrams obtained can be used both in filter material studies and in leak detection of valves or filter housings.”
“We conclude that the protection provided by surgical masks may be insufficient in environments containing potentially hazardous submicrometer-sized aerosols.”
“The filter efficiencies against influenza virus particles were the lowest”
“We conclude that the filter efficiency test using the phi-X174 phage aerosol may overestimate the protective performance of nonwoven fabrics with filter structure compared to that against real pathogens such as the influenza virus”
“We found that 60 GSM face mask had particle capture efficiency of 94% for total particles greater than 0.3 microns”
*Coronavirus is 0.125 microns.
Poor indoor quality transmission:
“From the sensitivity analysis, it shows that the transmission probability is strongly driven by indoor air quality, followed by patient infectiousness, and the least by respiratory protection from medical face mask use. Airborne infection transmission of pathogens such as measles virus and coronaviruses is likely to occur in the dental practice. The risk magnitude, however, is highly dependent on specific conditions in each dental clinic. Improved indoor air quality by ventilation, which reduces carbon dioxide, is the most important factor that will either strongly increase or decrease the probability of the transmission of a pathogen.”
“…The use of face masks, either by infected or non infected peresons, does not have a significant effect on influenza transmission.”
“…Although mechanistic studies support the potential effect of hand hygiene or face masks, evidence from 14 randomized controlled trials of these measures did not support a substantial effect on transmission of laboratory-confirmed influenza. We similarly found limited evidence on the effectiveness of improved hygiene and environmental cleaning. We identified several major knowledge gaps requiring further research, most fundamentally an improved characterization of the modes of person-to-person transmission.”
https://pubmed.ncbi.nlm.nih.gov/32582579/
As a result, masks surface become a contamination source. In the contact experiment, ten adults were requested to don and doff a surgical mask while doing a word processing task. The extended contamination areas were recorded and identified by image analysis. The results show an average contamination area of the workspace is significant 530 cm2. When the hand touches the surface of the mask, it may spread the virus to the subsequent contact area.
Exercising with masks not recommended:
“Exercising with facemasks may reduce available Oxygen and increase air trapping preventing substantial carbon dioxide exchange. The hypercapnic hypoxia may potentially increase acidic environment, cardiac overload, anaerobic metabolism and renal overload, which may substantially aggravate the underlying pathology of established chronic diseases. Further contrary to the earlier thought, no evidence exists to claim the facemasks during exercise offer additional protection from the droplet transfer of the virus. Hence, we recommend social distancing is better than facemasks during exercise and optimal utilization rather than exploitation of facemasks during exercise.”