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Reduction of Carbon Dioxide in Filtering Facepiece Respirators with an Active-Venting System: A Computational Study.

Birgersson E, Tang EH, Lee WL, Sak KJ - PLoS ONE (2015)

Bottom Line: 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%.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore.

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.

No MeSH data available.


Related in: MedlinePlus

Illustration of FFRs and the computational domains.(a) a standard FFR, (b) a FFR equipped with the blower of the AVS and (c-d) the computational domains comprising the dead space of the FFR, the filter and the blower; for the simulation of the standard FFR, the blower region was treated as a filter.
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pone.0130306.g001: Illustration of FFRs and the computational domains.(a) a standard FFR, (b) a FFR equipped with the blower of the AVS and (c-d) the computational domains comprising the dead space of the FFR, the filter and the blower; for the simulation of the standard FFR, the blower region was treated as a filter.

Mentions: In order to reduce the CO2 levels in the dead space to near-ambient levels, we introduce an active venting system (AVS) that aims to mimic and thus restore the functionality of the human respiratory system even when a FFR is covering our mouth and nostrils. In short, the lightweight AVS comprises a housing for a one-way valve, a blower and battery that can be attached to the FFR with negligible mechanical deformation of the filter. The blower illustrated in Fig 1 vents the air out from the FFR and should thus reduce the CO2 concentration inside the dead space.


Reduction of Carbon Dioxide in Filtering Facepiece Respirators with an Active-Venting System: A Computational Study.

Birgersson E, Tang EH, Lee WL, Sak KJ - PLoS ONE (2015)

Illustration of FFRs and the computational domains.(a) a standard FFR, (b) a FFR equipped with the blower of the AVS and (c-d) the computational domains comprising the dead space of the FFR, the filter and the blower; for the simulation of the standard FFR, the blower region was treated as a filter.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4482734&req=5

pone.0130306.g001: Illustration of FFRs and the computational domains.(a) a standard FFR, (b) a FFR equipped with the blower of the AVS and (c-d) the computational domains comprising the dead space of the FFR, the filter and the blower; for the simulation of the standard FFR, the blower region was treated as a filter.
Mentions: In order to reduce the CO2 levels in the dead space to near-ambient levels, we introduce an active venting system (AVS) that aims to mimic and thus restore the functionality of the human respiratory system even when a FFR is covering our mouth and nostrils. In short, the lightweight AVS comprises a housing for a one-way valve, a blower and battery that can be attached to the FFR with negligible mechanical deformation of the filter. The blower illustrated in Fig 1 vents the air out from the FFR and should thus reduce the CO2 concentration inside the dead space.

Bottom Line: 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%.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore.

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.

No MeSH data available.


Related in: MedlinePlus