A computational model for predicting changes in infection dynamics due to leakage through N95 respirators

Abstract

In the absence of fit-testing, leakage of aerosolized pathogens through the gaps between the face and N95 respirators could compromise the effectiveness of the device and increase the risk of infection for the exposed population. To address this issue, we have developed a model to estimate the increase in risk of infection resulting from aerosols leaking through gaps between the face and N95 respirators. The gaps between anthropometric face-geometry and N95 respirators were scanned using computed tomography. The gap profiles were subsequently input into CFD models. The amount of aerosol leakage was predicted by the CFD simulations. Leakage levels were validated using experimental data obtained using manikins. The computed amounts of aerosol transmitted to the respiratory system, with and without leaks, were then linked to a risk-assessment model to predict the infection risk for a sample population. An influenza outbreak in which 50% of the population deployed respirators was considered for risk assessment. Our results showed that the leakage predicted by the CFD model matched the experimental data within about 13%. Depending upon the fit between the headform and the respirator, the inward leakage for the aerosols ranged between 30 and 95%. In addition, the non-fit-tested respirator lowered the infection rate from 97% (for no protection) to between 42 and 80%, but not to the same level as the fit-tested respirators (12%). The CFD-based leakage model, combined with the risk-assessment model, can be useful in optimizing protection strategies for a given population exposed to a pathogenic aerosol.

A Simple Method to Quantify Outward Leakage of Medical Face Masks and Barrier Face Coverings: Implication for the Overall Filtration Efficiency

“…Particularly when talking, the number of particles captured by the mask increased at a rate of about 5% per L/min [ 45 ], suggesting that less aerosol was leaked. Similar conclusions were drawn by Hariharan et al, who investigated the particle leakage with different respirators, measuring a reduction from 17–22% to 4% when the flow rate was increased from 10 L/min to 70 L/min [ 46 ]. Tang et al studied the turbulent jet caused by coughing and suggested that, according to the typology of the mask worn, it is possible to thwart the trajectory of the jet, directing airflow towards the boundaries of masks with poor fit [ 47 ].…”

Effects of surgical masks on aerosol dispersion in professional singing

“…Similar observations were reported for breathing, coughing and sneezing by using human subjects [ 24 , 33 , 50 ], manikin model [ 22 , 23 , 39 , 53 ] or CFD models [ 26 ]. Furthermore, leakages were also found for KN95 or N95 masks [ 25 , 42 , 55 , 56 ]. Especially in closed rooms without effective ventilation, exhaled aerosol particles can accumulate and develop a critical concentration if single persons are infected.…”

In Silico Fit Evaluation of Additively Manufactured Face Coverings

“…These values are subsequently summed to calculate the leakage gap surface area. 8,13 The following measures are used to assess the fit for various frame designs (1) contact gap profile between the face mask and the headform and (2) surface area of the leakage gap created due to imperfect fit.…”