Aimo Taipale

Electrospun PA-66 Coating on Textile Surfaces:

Electrospinning was used to produce lightweight coatings of polyamide-66 nanofibers on different fibrous substrates. Filtration efficiency of coated and uncoated samples and strain capacity of the nanofiber layer were tested. Filtration efficiency clearly increased even with the lowest amount of nanofibers (0.02 g/m2) when compared to uncoated samples, and with the highest nanofiber coating weight (0.5 g/m2) the filtration efficiency of submicron aerosol particles was over 90%. Elongation capacity of the polyamide nanofiber layer was found to be insufficient to be used with elastic materials. The polyamide nanofiber layer is, therefore, suitable to be used with relatively rigid substrate e.g. spunbond nonwoven and at least thicker nanofiber layers are advisable to be protected with cover layer, because the nanofiber layer also delaminates easily from the textile surface.

Filter clogging by bimodal aerosol

Pressure drop evolution during filtration of bimodal aerosol was studied experimentally. A low-pressure drop pre-filter upstream of the actual collection filter was demonstrated to significantly reduce the pressure drop growth rate, when the aerosol is dominated by coarse particles. The pressure drop evolution during depth-filtration, that took place mainly in a pre-filter, could be predicted by adding up the separately measured contributions from the unimodal fine and coarse aerosols. However, the cake filtration (pre-filter was not used) of coarse particles alone resulted in a faster clogging rate as compared to the same amount of coarse particles accompanied with fine particles (mass ratio coarse:fine 3:1). Apparently, fine particles deposited on coarse particles affect their surface properties and thus the porosity of the cake formed.

Performance of ventilation filtration technologies on characteristic traffic related aerosol down to nanocluster size

ABSTRACT Near traffic routes and urban areas, the outdoor air particle number concentration is typically dominated by ultrafine particles. These particles can enter into the nearby buildings affecting the human exposure on ultrafine particles indoors. In this study, we demonstrate an aerosol generation system which mimics the characteristic traffic related aerosol. The aerosol generation system was used to determine the size-resolved particle filtration efficiencies of five typical commercial filters in the particle diameter range of 1.3–240 nm. Two different HEPA filters were observed to be efficient in all particle sizes. A fibrous filter (F7) was efficient at small particle sizes representing the nucleation mode of traffic related aerosol, but its efficiency decreased down to 60% with the increasing particle size. In contrast, the filtration efficiency of an electrostatic precipitator (ESP) increased as a function of the particle size, being more efficient for the soot mode of traffic related aerosol than for the nucleation mode. An electret filter with a charger was relatively efficient (filtration efficiency >85%) at all the observed particle sizes. The HEPA, F7 and electret filters were found to practically remove the particles/nanoclusters smaller than 3 nm. All in all, the filtration efficiencies were observed to be strongly dependent on the particle size and significant differences were found between different filters. Based on these results, we suggest that the particulate filter test standards should be extended to cover the ultrafine particles, which dominate the particle concentrations in outdoor air and are hazardous for public health. Copyright

Celebrating 30 years of conference series on industrial ventilation-health, comfort and efficiency

In 1985, the industrial ventilation conference series (hereafter referred to as Ventilation) was initiated by Dr Howard D. Goodfellow in Toronto, as an important step to raise the level of industrial ventilation worldwide. Since then, the conference has been held triennially in London (England, 1988), Cincinnati, Ohio (U.S.A., 1991), Stockholm (Sweden, 1994), Ottawa (Canada, 1997), Helsinki (Finland, 2000), Sapporo (Japan, 2003), Chicago (U.S.A., 2006), Zurich (Switzerland, 2009) and Paris (France, 2012). The Ventilation conferences have been the premier international meeting place for scientists and professionals in the field of ventilation sciences and technologies. The 11th conference, Ventilation 2015, was held in Shanghai. It was jointly organised by Tongji University, Technical Research Centre of Finland (VTT) and Tsinghua University. The theme of the conference was ‘Celebrating 30 Years of Conference Series on Industrial Ventilation-Health, Comfort and Efficiency.’ One hundred and twenty-four papers were peer-reviewed and delivered by the authors from 15 countries and regions in 14 parallel sessions and 2 poster sessions. These papers covered various aspects on occupational health, ventilation and sustainable development, industrial ventilation and pollutant control, air distribution design, measurement and products and specialised applications. Thirty years of devotion is not a short time for one’s career, and it is a remarkable achievement to successfully organise a conference series for 30 years. When we start to look back, the rapid progresses in understanding and applying ventilation technologies have significantly improved workplace environment for hundreds and thousands of production lines. Design guidelines, standards or even legislations to support industrial ventilation have been proposed and implemented in many countries worldwide. Meanwhile, ventilation demands and solutions for non-industrial environment have also been developed at a high rate. The typical focuses of ventilation have been changed from preventing environmental pollution and guaranteeing high product quality to ensuring people’s health, comfort and productivity. To date, unsurprisingly, the majority of ventilation researches and innovations are usually in the non-industrial domain. The Ventilation conference was also adapted to this trend and embraced more general ideas and technologies for ventilation in non-industrial indoor environment. It is not a wrong thing to emphasise the need of ventilation in offices and residences, since in many countries, less and less people are working in hostile environment today compared to the number 30 years ago. However, some of you might have heard of the tragedy about the massive dust explosion occurred at an automotive parts factory located in Kunshan, Jiangsu Province, China, on 2 August 2014. By far, the explosion killed at least 146 workers and injured 114 others. One of the major reasons was believed that the factory was lacking ventilation equipment and the explosion may have been caused by flames igniting metal polishing dusts. This 2014 Kunshan explosion reminded us that ventilation, especially industrial ventilation, is not only an auxiliary means for keeping us comfort or manufacturing better products, it also can be the last straw to protect us from real dangers. Industrial ventilation has been never an outdated topic. It is always an essential and comprehensive work to improve the air quality for workplace environment in factories and plants since to minimise the health risks posed on occupants from various (and many) materials and processes is a