DETERMINATION OF BREATHING RESISTANCE ACROSS ACTIVATED CARBON FIBER RESPIRATOR CARTRIDGES USING SINUSOIDAL AIRFLOW

Abstract

Activated carbon fibers are considered good alternative adsorbents in respirators because of their high adsorption capacities, light weight, and fabric form. In order to further assess such application, the pressure drop across Activated carbon fibers in respirators must be adequately low to allow comfortable breathing of the wearer. This study investigated the pressure drop, PD across Activated carbon fibers in respirator cartridges using realistic breathing patterns. Two forms of Activated carbon fibers, cloth, ACC and felt, ACN were tested at three different surface areas: 1000, 1500 and 2000 g/m². Each Activated carbon fiber was placed in respirator cartridge at three different layers and subjected to two patterns of breathing: 20 litres per minute by 20 breaths per minute, and 68 litres per minute by 20 breaths per minute from a dynamic breathing machine supplied with purified air at 23°C and 50% relative humidity. PD determination was carried out in a customized Teflon testing chamber. Woven ACC was composed of closely knitted fibers while the unwoven ACN was composed of gradually distributed fibers. The individual effect of Activated carbon fibers forms, layers, breathing patterns, and surface areas was significant on inhalation and exhalation PD. Inhalation and exhalation PD were not significantly different, P=0.446 and P=0.736, respectively between the two forms. Increasing airflow in a single respirator cartridge to 68 LPM significantly increased inhalation PD, P<0.001 and exhalation PD, P<0.001 compared to PDs measurements obtained from 20 x 20 breathing pattern. Differences in inhalation and exhalation PD of the surface areas were not significant, P=0.647 and P=0.665. Increasing the Activated carbon fibers layers significantly increased both inhalation PD, P=0.016 and exhalation PD, P<0.001. This observation suggest an optimum layer for Activated carbon fibers' use in respiratory protection also, respirator certification testing using 68 litres per minute sinusoidal airflow may simulate strenous activities in work place better. It is concluded that Activated carbon fibers' forms, number of layers, breathing pattern and surface area are all important individual factors in designing a breathable respirator cartridge.