Filtration performance of ultrathin electrospun cellulose acetate filters doped with TiO₂ and activated charcoal

Air filters are crucial components of a building ventilation system that contribute to improving indoor air quality, but they are typically associated with relatively high pressure drops. The purpose of the study is to evaluate the effect of additives on ultrathin electrospun filters, the pressure drop, and the particle removal efficiency of uniformly charged particles. The fibres were electrospun under optimised conditions that resulted in a fast-fabricating process due to the properties of the cellulose acetate solution. Different ultrathin electrospun fibre filters based on cellulose acetate (CA) were fabricated: a pure CA electrospun fibre filter, two filters based on CA fibres separately doped with activated charcoal (AC) and titanium dioxide (TiO2), respectively, and a composite filter where the two additives, AC and TiO2, were embedded between two CA fibres layers. The ultrathin filters exhibited a low pressure drop of between 63.0 and 63.8 Pa at a face velocity of 0.8 m s−1. The filtration performance of uniformly charged particles showed a removal efficiency above 70% for particle sizes between 0.3 and 0.5 μm for all filters, rising above 90% for larger particles between 1 and 10 μm, which translates to the average sizes of pollens and other allergenic contaminant particles. Due to the positive impact on the fibre morphology caused by the additives, the composite filter showed the highest filtration performance among the produced filters, reaching 82.3% removal efficiency towards smaller particles and a removal of up to 100% for particle sizes between 5 and 10 μm. Furthermore, cellulose acetate itself is not a source of microparticles and is fully biodegradable compared to other polymers commonly used for filters. These ultrathin electrospun filters are expected to be practical in applications for better building environments

Reducing Health Risks from Indoor Exposures in Rapidly Developing Urban China.

Background: Over the past two decades there has been a large migration of China’s population from rural to urban regions. At the same time, residences in cities have changed in character from single-story or low-rise buildings to high-rise structures constructed and furnished with many synthetic materials. As a consequence, indoor exposures (to pollutants with outdoor and indoor sources) have changed significantly. Objectives: We briefly discuss the inferred impact that urbanization and modernization have had on indoor exposures and public health in China. We argue that growing adverse health costs associated with these changes are not inevitable, and we present steps that could be taken to reduce indoor exposures to harmful pollutants. Discussion: As documented by China’s Ministry of Health, there have been significant increases in morbidity and mortality among urban residents over the past 20 years. Evidence suggests that the population’s exposure to air pollutants has contributed to increases in lung cancer, cardiovascular disease, pulmonary disease, and birth defects. Whether a pollutant has an outdoor or an indoor source, most exposure to the pollutant occurs indoors. Going forward, indoor exposures can be reduced by limiting the ingress of outdoor pollutants (while providing adequate ventilation with clean air), minimizing indoor sources of pollutants, updating government policies related to indoor pollution, and addressing indoor air quality during a building’s initial design. Conclusions: Taking the suggested steps could lead to significant reductions in morbidity and mortality, greatly reducing the societal costs associated with pollutant derived ill health

Electrostatic Precipitators as an Indoor Air Cleaner: A Literature Review

Many people spend most of their time in an indoor environment. There is a positive relationship between indoor environmental quality and the health, wellbeing, and productivity of occupants in buildings. The indoor environment is affected by pollutants, such as gases and particles. Pollutants can be removed from the indoor environment in various ways. Air cleaning devices are commonly marketed as benefitting the removal of air pollutants and consequently, improving indoor air quality. Depending on the type of cleaning technology, air cleaners may generate undesired and toxic by-products. Different air filtration technologies such as electrostatic precipitators have been introduced to the market. The electrostatic precipitator (ESP) has been used in buildings because it can remove particles while only causes low pressure drops. Electrostatic precipitators can be either in-duct or standalone units. This review aims to give an overview of ESP use, methods for testing this product, the performance of existing ESPs in removing pollutants, their by-products, and the existing market for ESPs

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

One-year dataset of hourly air quality parameters from 100 air purifiers used in China residential buildings

Household air purifiers have been widely used as an effective approach to improving indoor air quality. Air purifiers can automatically record indoor air quality parameters, providing valuable data resources for in-depth data-driven analysis. This work presents a one-year hourly indoor air quality dataset collected by household air purifiers in 100 residential homes in 18 provinces across 4 different climate zones in China. The data were collected from July 1, 2021, to July 1, 2022. The concentrations of formaldehyde, PM2.5, TVOC, temperature, relative humidity, on/off status and the airflow rate of air purifiers during operations were recorded hourly.</p

Prediction and validation of diffusive uptake rates for indoor volatile organic compounds in axial passive samplers

The diffusive uptake rate is essential for using passive samplers to measure indoor volatile organic compounds (VOCs). The traditional theoretical model of passive samplers requires available regression formulas of uptake rates and physicochemical properties of adsorbents to predict the uptake rate. However, it is difficult to obtain the uptake rates of different VOCs under different sampling periods, and it is also difficult to obtain the physical parameters of adsorbents accurately and effectively. This study provides a reliable numerical prediction method of diffusive uptake rates of VOCs. The modeling was based on the standard automated thermal desorption (ATD) tubes packed with Tenax TA and the mass transfer process during adsorption. The experimental determinations of toluene uptake rate are carried out to verify the prediction model. Diffusive uptake rates of typical indoor VOCs are obtained from the literature to calibrate the key apparent parameters in the model by statistical regression fitting. The predicted model can provide the VOC diffusive uptake rates under different sampling duration with an average deviation of less than 5%. This study can provide the basis for fast and accurate prediction of diffusive uptake rates for various VOC pollutants in built environments