Face masks and respirators in the fight against the COVID-19 pandemic: An overview of the standards and testing methods.

The COVID-19 outbreak has resulted in a shortage of personal protective equipment (PPE) throughout the world. This shortage has resulted in an increase in production of PPE to meet the demand, and as a result, several substandard equipment has entered the market. With face masks and respirators now beginning to see widespread use throughout the world, the standards and test with which they are required to undertake have become points of interest. The filtration efficiency of the masks is a key testing element that examines its ability to filter particles, bacteria and viruses; this examines the penetration efficiency percentage of each with lower results being preferable. Masks are also subjected to NaCl testing method, which allows a range of particle sizes to be examined and their penetration to be observed. The masks must also show considerable resistance to fluids and flames, to prevent the penetration of liquids and to be non-flammable. Various PPE testing protocols such as biological, chemical, fluid and flame resistances, protective ensemble, facepiece fit testing, NIOSH NaCl method and impact protection have been discussed. In addition, various tests involving bacterial and viral filtration efficiencies are also discussed. Differential pressure is examined to ascertain the comfort, airflow and breathability of the masks, whilst fit testing is examined to ensure a correct fit of the mask.

Face Masks and Respirators in the Fight against the COVID-19 Pandemic: A Review of Current Materials, Advances and Future Perspectives.

The outbreak of COVID-19 has spread rapidly across the globe, greatly affecting how humans as a whole interact, work and go about their daily life. One of the key pieces of personal protective equipment (PPE) that is being utilised to return to the norm is the face mask or respirator. In this review we aim to examine face masks and respirators, looking at the current materials in use and possible future innovations that will enhance their protection against SARS-CoV-2. Previous studies concluded that cotton, natural silk and chiffon could provide above 50% efficiency. In addition, it was found that cotton quilt with a highly tangled fibrous nature provides efficient filtration in the small particle size range. Novel designs by employing various filter materials such as nanofibres, silver nanoparticles, and nano-webs on the filter surfaces to induce antimicrobial properties are also discussed in detail. Modification of N95/N99 masks to provide additional filtration of air and to deactivate the pathogens using various technologies such as low- temperature plasma is reviewed. Legislative guidelines for selecting and wearing facial protection are also discussed. The feasibility of reusing these masks will be examined as well as a discussion on the modelling of mask use and the impact wearing them can have. The use of Artificial Intelligence (AI) models and its applications to minimise or prevent the spread of the virus using face masks and respirators is also addressed. It is concluded that a significant amount of research is required for the development of highly efficient, reusable, anti-viral and thermally regulated face masks and respirators.

Photo-Fenton disinfection at near neutral pH: Process, parameter optimization and recent advances

The photo-Fenton process is an advanced oxidation process that uses the hydroxyl radical to disinfect and decontaminate water. Its non-selectivity makes it ideal for the removal of a range of microorganisms including those with antimicrobial resistance. Optimum parameters such as pH, temperature, hydrogen peroxide and iron concentrations and the intensity and wavelength of light irradiation are important to carry out an efficient photo-Fenton process. Traditionally photo-Fenton has been carried out at low acidic pH to obtain greater efficiency, but recent studies have been performed at near neutral. The current review examines the effectiveness of the photo-Fenton process at a near neutral pH for the disinfection of water. The optimal pH was seen to be at 2.8, with the efficiency of the photo-Fenton process decreasing as the pH rises. The optimal reagent concentrations showed considerable variation depending on the iron catalyst used and the iron to hydrogen peroxide concentration used. The effect of irradiance and temperature showed improved efficiency with higher levels. Different types of microorganisms such as E. coli, Pseudomonas sp., Enterococcus faecalis, Klebsiella pneumonia, Salmonella spp., total Coliforms, MRSA, MSSA, B. subtilis, Clostridium sp., Faecal Coliform, MS2 coliphage and Curvularia sp. are also examined and the effect the process will have on them. The design of reactors, such as compound parabolic reactors are also examined. The impact of light sources, including the recent reports on LEDs, on the production of hydrogen peroxide and thereby the improvement in the overall photo-Fenton disinfection is also discussed in detail. Finally, a techno-economic analysis to explain various costs associated with photo-Fenton process has also been carried out. It is concluded that the development of new heterogeneous supported immobilised catalysts that could work at the near neutral pH is an area, which require considerable future research.