Performance of N95 elastomeric respirators in high humidity and high coal dust concentration environment

High humidity and high dust concentration in deep coal mines may severely challenge the performance of respirators worn by coal miners.This paper aims at quantitatively evaluating the respirators used in deep coal mines and providing scientific guidance for the respiratory protection of miners.Based on the self-designed in-situ PM2.5 collector,controllable PM2.5 generator,human breathing simulator,and respirator simulation testing system,under the simulated deep mine working condition,this study investigated the effects of dust loading,wearing time,and dust concentration on the filtration efficiency,breathing resistance,and quality factor of N95 elastomeric respirators.With the increase of dust loading,the respirator filtration efficiency firstly decreased,then increased(minimum value 97.5%).The breathing resistance increased exponentially from 120 to 180 to 1020-1530 Pa,and the quality factor decreased logarithmically from 0.051 to 0.076 to 0.0058-0.0085 Pa^(-1).As the PM2.5 coal dust concentration increased from 5 to 50 mg/m^(3),the wearing time for the respirator breathing resistance to exceed 300 Pa reduced from 7 h to less than 1 h.One N95 elastomeric respirator is not able to perform an 8-h work shift.To avoid the excessive breathing resistance caused by dust loading,more filter cartridges are needed for coal miners.

Semi-analytical and computational investigation of different dust loading structures affecting the performance of a fibrous air filter

In this study, a semi-analytical model was developed to illustrate the relationship between filtration performance （filtration efficiency and pressure drop） and dust loading under two different particle deposit structures based on theoretical analysis and computational fluid dynamic （CFD） technology. Under the compact deposit structure, within the practical parameter ranges （fiber diameter, air velocity, dust loading mass）, a slight efficiency enhancement （∽10%） occurred at the most penetration particle size （MPPS） and pressure drop increased significantly （∽100%） in response to the solidity increase from 5% to 15%. However, under the dendritic particle deposit structure, both filtration efficiency （∽40%） and pressure drop （4600%） increased significantly with the same solidity increase due to the larger air velocity and swerve change between fibers.

Effects of road dust on the growth characteristics of Sophora japonica L.seedlings

Road dust is one of the most common pollutants and causes a series of negative effects on plant physiology. Dust＇s impacts on plants can be regarded as a combination of load,composition and grain size impacts on plants; however, there is a lack of integrated dust effect studies involving these three aspects. In our study, Sophora japonica seedlings were artificially dusted with road dust collected from the road surface of Beijing so that we could study the impacts of this dust on nitrogen/carbon allocation, biomass allocation and photosynthetic pigments from the three aspects of composition, load and grain size. The results showed that the growth characteristics of S. japonica seedlings were mostly influenced by dust composition and load. Leaf N, root–shoot ratio and chlorophyll a/b were significantly affected by dust composition and load; leaf C/N, shoot biomass, total chlorophyll and carotenoid were significantly affected by dust load; stem N and stem C/N were significantly affected by dust composition; while the dust grain size alone did not affect any of the growth characteristics. Road dust did influence the growth characteristics more extensively than loam. Therefore, a higher dust load could increase the differences between road dust and loam treatments. The elements in dust are well correlated to the shoot N, shoot C/N, and root–shoot ratio of S. japonica seedlings. This knowledge could benefit the management of urban green spaces.

Initial results for urban metal distributions in house dusts of Syracuse,New York,USA

A program of house dust sample collection and analysis has begun in Syracuse,New York,USA,in order to determine the feasibility of a geography-based exposure assessment for urban metals.The sampling program,and the protocols it employs,is described for two different types of wipe media,Ghost Wipes and Whatman Filters.Preliminary results show that strong spatial patterns of floor dust loading(mg dust per square foot)can be observed for data aggregated at a spatial scale of about 1600 m(~2.5 km^(2)).Floor dust metal concentrations were similar to those found in other urban environments,with some regional variation.The median floor dust Pb concentration was~108 mg·kg^(-1)for this initial data set of~264 sampled residential locations,and varied from 50 to 1100 mg Pb·kg^(-1).

Simulation of Bimodal Fiber Distribution Effect on Transient Accumulation of Particles During Filtration

Modeling has become phenomenal in developing new products.In the case of filters,one of the mos applied procedures is via the construction of idealized physical computational models bearing close semblance to real filter media.It is upon these that multi-physics tools were applied to analvze the fow of fuid and the resulting typical performance parameters.In this work,two 3D filter membranes were constructed with MATLAB:one had a random distribution of unimodal nanofibers,and the other,a novel modification,formed.a bimodal distribution:both of them had similar dimensions and solid volume fractions.A comparison of their performance in a dust-loading environment was made by using computational fluid dynamic-discrete elemen method(CED-DEM)coupling technique in STAR-CCM+.It was found that the bimodal nanofiber membrane greatly improved the particle capture efficiencv.Whereas this increased the pressure drop,the gain was not toosignificant.Thus.overall,the results of the figure of merit ptoved that adopting a bimodal formation improved the filter's quality.