Abstract
During expiration, the carbon dioxide (CO2) levels inside the dead space of a filtering facepiece respirator (FFR) increase significantly above the ambient concentration. To reduce the CO2 concentration inside the dead space, we attach an active lightweight venting system (AVS) comprising a one-way valve, a blower and a battery in a housing to a FFR. The achieved reduction is quantified with a computational-fluid-dynamics model that considers conservation of mass, momentum and the dilute species, CO2, inside the FFR with and without the AVS. The results suggest that the AVS can reduce the CO2 levels inside the dead space at the end of expiration to around 0.4% as compared to a standard FFR, for which the CO2 levels during expiration reach the same concentration as that of the expired alveolar air at around 5%. In particular, during inspiration, the average CO2 volume fraction drops to near-to ambient levels of around 0.08% with the AVS. Overall, the time-averaged CO2 volume fractions inside the dead space for the standard FFR and the one with AVS are around 3% and 0.3% respectively. Further, the ability of the AVS to vent the dead-space air in the form of a jet into the ambient – similar to the jets arising from natural expiration without a FFR – ensures that the expired air is removed and diluted more efficiently than a standard FFR.
Highlights
The form and function of the human respiratory system ensures an efficient gas exchange with the environment
Once we add the active lightweight venting system (AVS) with a view to restore the functionality of respiration, we reduce the CO2 level significantly as expected in Fig 4: the CO2 levels do no increase monotonically during expiration, as was the case for the standard filtering facepiece respirator (FFR), but rather peak around 2% and drop towards 0.4% at the end of expiration
We have carried out CFD simulations for quiet breathing through a standard FFR and one equipped with an AVS
Summary
The form and function of the human respiratory system ensures an efficient gas exchange with the environment. The physical phenomena associated with respiration and passive transport of CO2 are captured via the equations of change for turbulent and laminar momentum in the dead space and filter respectively and for mass and the species CO2, boundary conditions and constitutive relations for the breathing cycle, expired carbon dioxide, filter and blower. These are based on the following main underlying assumptions and characteristics: 1. We note that the fitted permeability is of the same order of magnitude as that employed by Lei et al [14]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
