Research on Regularities of Cyclic Air Motion through a Respirator Filter

Abstract

In this paper, a solution to the problem of the change in the pressure drop in a respirator filter during cyclic air motion is suggested since the current theory of filtering is based on steady-flow processes. The theoretical dependence of the pressure drop in the respirator filter on air flow rate is determined, which is represented by the harmonic law, which characterizes the human respiration process during physical work. For the calculation, a filter model was used, which is represented by a system of parallel isolated cylinders with a length equal to the total length of the filter fibres surrounded by porous shells formed by a viscous air flow field, with a size determined by the equal velocities of the radial component of air flow and undisturbed flows. The flow-around process in the proposed model of air flow through the respirator filter is described by the Brinkman equation, which served to establish the total air flow resistance in the proposed system under conditions of velocity proportionality. It consists of two parts: the first characterizes the frictional resistance of the air flow against the surface of the cylinder, which imitates the filter fibre; the second—the inertial part—characterizes the frequency of pulsations of respiratory movements during physical performance. The divergence of the analytical results and experimental studies is no more than 20%, which allows the use of the established dependence to estimate the change in pressure drop in a respirator filter made of filter material “Elephlen” when the user carries out different physical activities. This allows the period of effective protective action of respirators with different cycles of respiration during physical activities to be specified, which is a very serious problem that is not currently regulated in health and safety regulations, and it also allows the prediction of the protective action of filters and respiratory protection in general.

Overview of tight fit and infection prevention benefits of respirators (filtering face pieces)

“…From the point of view of occupational health and safety requirements, the most important factor for the protection of a person by wearing a disposable respirator is the tight fit of the respirator [ 1 , 2 ], even during physical activity, which is associated with the protective effect. In the technical development, approval and quality control of disposable respirators, a standardized pliable elastomeric head form is regularly used (Sheffield dummy head), which represents male European facial dimensions [ 12 , 13 ]. This dummy does not represent the diversity of people working in the healthcare sector around the world including their variable head forms and is likely to have a non-negligible effect on fit test results of commercially available respirators.…”

Mathematical model of air flow movement in a motorized filter respirator

“…Thus, taking into account equations (6)(7)(8), we obtain a sys tem of equations that describes the air flow in the MFR air duct…”

“…One of such tasks is to ensure effective regulation of sup plying the necessary volume of air to the user, taking into ac count the pressure limitations in the MFR mask [5,6], based on changes in working conditions, the degree of physical exer tion on the user or their emotional state during the perfor mance of professional functions, contamination of MFR fil ters, and increase in their resistance to airflow [7,8], climatic conditions (temperature and humidity of the air) in the work ing area [9], and other parameters that characterize the influ ence on the quality indicators of RPE and may reduce their protective efficiency and level of comfort during the perfor mance of tasks of varying intensity [10].…”

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“…Comparable conclusions were reached by O. Bazaluk et al (2021), who recommended to abandon ventilators with a voltage of 12 V and switch to models powered by a voltage of 24 V. However, this requires an increase in the capacity of the battery, and therefore its weight, which will affect the performance of the user of the motorized filter respirator. There is a need to create a suitable algorithm for testing various modes of operation of a motorized filter respirator to establish clear time frames for its operation in diverse production conditions.…”