Simultaneously reducing CO2 and particulate exposures via fractional recirculation of vehicle cabin air
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Simultaneously reducing CO2 and particulate exposures via fractional recirculation of vehicle cabin air

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  • Alternative Title:
    Atmos Environ (1994)
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    Prior studies demonstrate that air recirculation can reduce exposure to nanoparticles in vehicle cabins. However when people occupy confined spaces, air recirculation can lead to carbon dioxide (CO|) accumulation which can potentially lead to deleterious effects on cognitive function. This study proposes a fractional air recirculation system for reducing nanoparticle concentration while simultaneously suppressing CO| levels in the cabin. Several recirculation scenarios were tested using a custom-programmed HVAC (heat, ventilation, air conditioning) unit that varied the recirculation door angle in the test vehicle. Operating the recirculation system with a standard cabin filter reduced particle concentrations to 1000 particles/cm|, although CO| levels rose to 3000 ppm. When as little as 25% fresh air was introduced (75% recirculation), CO| levels dropped to 1000 ppm, while particle concentrations remained below 5000 particles/cm|. We found that nanoparticles were removed selectively during recirculation and demonstrated the trade-off between cabin CO| concentration and cabin particle concentration using fractional air recirculation. Data showed significant increases in CO| levels during 100% recirculation. For various fan speeds, recirculation fractions of 50-75% maintained lower CO| levels in the cabin, while still reducing particulate levels. We recommend fractional recirculation as a simple method to reduce occupants' exposures to particulate matter and CO| in vehicles. A design with several fractional recirculation settings could allow air exchange adequate for reducing both particulate and CO| exposures. Developing this technology could lead to reductions in airborne nanoparticle exposure, while also mitigating safety risks from CO| accumulation.
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