Volatile organic compounds (VOCs) emitted by building materials pose severe health risk. It is critical to identify major pollution sources for consequent intervention. An in-situ sampling method is introduced in this study to determine solid–gas interface concentrations of building materials to help realize source apportionment with minimal disturbance and cost. The method is featured as an upended cylindrical chamber with two openings. A sampling flow rate lower than a critical value allows diffusion-controlled environment in the chamber and concentration equilibrium between building surfaces and the air. It is validated by tests under various sampling flow rates (difference of 2%–11%) and in an enclosed chamber (difference of 4.7%–14%). Flow field analysis shows that air speed in the chamber is lower than 0.001 m/s and Reynolds number is smaller than 0.5, confirming the diffusion nature. Results indicate that a chamber with large bottom area and/or low height could have high acceptable sampling flow rate, which would reduce sampling time needed. A field test demonstrated that the method can reasonably help reconstruct pollution field and capture interface concentrations change along with temperature. The proposed in-situ method could facilitate better diagnose indoor air pollution by quantifying source contributions.

Adverse impacts of exposure to formaldehyde on human health significantly increases attention in monitoring formaldehyde concentrations in the air. Conventional formaldehyde detection methods typically rely on large and costly instruments and requires high skills of expertise, preventing it from being widely accessible to civilians. This study introduced a novel approach utilizing smartphone-based colorimetric analysis. Changes of green channel signals of digital images by a smartphone successfully capture variation of purple color of 4-amino-3-hydrazino-5-mercapto-1,2,4-triazol solution, which is proportional to formaldehyde concentrations. It is because that green and purple are complimentary color pairs. A calibration curve was established between green channel signals and formaldehyde concentrations, with a correlation coefficient of 0.98. Detection limit of the smartphone-based method is 0.008 mg/m³. Measurement errors decrease as formaldehyde concentrations increase, with median relative errors of 34%, 17%, and 6% for concentration ranges of 0–0.06 mg/m³, 0.06–0.12 mg/m³, and 0.12–0.35 mg/m³, respectively. This method replaced scientific instrumentation with ordinary items, greatly reducing cost and operation bars. It would provide an opportunity to realize onsite measurements for formaldehyde by occupants themselves and increase awareness of air quality for better health protection.

Considering that people spend more than 80% of their time indoors, ambient particulate matter (PM) in the built environment could pose severe environmental health risks to public health. PM sampling, a technique for the enrichment of PM in the air, is essential for ambient PM composition analysis to understand its environmental and health effect. The filtering method that is widely used features a complex post-processing and carries the risk of pore clogging. It is a great challenge to sample airborne PM efficiently for subsequent analysis. Here, we proposed a novel miniaturized electrostatic sampler based on corona discharge and a modified vertically focused electric field for efficient PM sampling. Four intercoupling physical fields in the developed sampler were analyzed, including corona discharge, airflow, particle charging and particle deposition. The collection efficiencies for particles with various sizes (0.01–10 μm) were conducted by simulation and the lowest efficiency occurs at about 0.3–0.5 μm. With an increase in discharging voltage from −6 kV to −9 kV, the lowest efficiency rises from 88.2% to 96.6%. An electrostatic sampler entity was manufactured to test the collection efficiency of PM and the results are in good agreement with the simulation. The induced ring plate can significantly improve the total collection efficiency from 35% to 90% under −6 kV discharging voltage in the experiment. The novel electrostatic sampler exhibits potential and enlightenment for efficient and convenient PM sampling.

Air infiltration is an important way to exchange indoor air with outdoors. It significantly impacts energy consumption and air quality of buildings. Fine particles (PM_2.5) in the outdoor atmosphere environment are a potential natural tracer for the measurement of air infiltration rate, especially in the long term field measurement. In this study, a PM_2.5-based method, named as CADR (clean air delivery rate) method, is developed to supplement traditional tracer gas method in order to make routine measurement in realistic environments possible and convenient. An air cleaner is installed indoors to reduce indoor PM_2.5 concentration. Air infiltration is determined by fitting a model to the decreasing concentration data. Comparison with CO₂ decay method in four different indoor environments gives a normalized mean error of 19% and a correlation coefficient of 0.80 for this method. This justifies the CADR method as a feasible option to measure air infiltration rate. Although subject to several constraints, the proposed method would facilitate field measurement under realistic conditions by being combined with current tracer gas methods.