Abstract
Urban coach cabin is an important indoor environment for long journey, formaldehyde (HCHO) is a carcinogenic gas and damages indoor air quality of cabins. In order to control the HCHO pollution, the air samples inside cabins were analysed with a thermally desorbed gas chromatograph, and the HCHO diffusion was simulated with a methodology of computational fluid dynamics (CFD). Results show that through the experimental monitoring, the HCHO pollution level range from 33.6 to 142.3 μg/m3, decrease quickly with time, and the attenuation trendline is univariate cubic equation. Through the CFD simulation, the indoor temperature and HCHO level of cabin front and rear ends are higher than ones of other areas for the insufficient air supply and the unreasonable arrangement of air exhaust outlet. Moreover, through the CFD simulation, the HCHO level decreases with height growth of breathing zone and increasing air supply speed, and fresh air lead to diffusion of HCHO pollution from cabin seat area to the surrounding area. Through the CFD simulation, the HCHO pollution under the wind speeds of 3~5 m/s is higher than the HCHO limit level from indoor air standard of China vehicles, which shows that the HCHO emission of cabin seat has an important impact on airborne HCHO pollution inside vehicle cabins.
Highlights
According to the year 2017 statistic bulletin of traffic industry development from the Transportation Ministry of China, the total of urban vehicles was 3.1 × 108 and the annual capacity of passengers transported by the vehicles was 7.2 × 1011
The reason for the difference of HCHO concentration is the difference of coach brand, coach age, sampling location, cabin indoor temperature and relative humidity
For the HCHO and volatile organic compounds (VOCs) pollution mainly comes from cabin indoor materials including leather trims, organic solvents, paints, adhesives and so on[11,12,13,25]
Summary
According to the year 2017 statistic bulletin of traffic industry development from the Transportation Ministry of China, the total of urban vehicles was 3.1 × 108 and the annual capacity of passengers transported by the vehicles was 7.2 × 1011. In order to decrease the health risks, China government promulgated the hygienic standard for air quality inside long distance coach (GB/T 17729–2009) and the guideline for air quality assessment of passenger car (GB/T 27630–2011), with the HCHO limit levels of 0.12 and 0.10 mg/m3 respectively. The average/maximal HCHO levels in car cabins were 132.0/251.6 μg/m3, which were 1.10/2.10 and 1.32/2.52 times more than the HCHO limit levels of IAQ standards on China coaches (GB/T 17729-2009) and passenger cars (GB/T 27630-2011) respectively[20]. There is few reports about the numerical simulation of airborne HCHO pollution in vehicle cabins, and the less is known about the effect of different breathing zone (horizontal plane), air temperature and ventilation conditions on the HCHO pollution. The coach age, exhaust volume and total driving mileage were 2.5 years, 3.6 liters and 5.9 × 104 km respectively
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