How indoor air quality affects the temporal associations of long-term exposure to low-level air pollutants with cognition remains unclear. This cohort study (2011-2019) included 517 non-demented older adults at baseline with four repeated cognitive assessments. The time-varying exposure to PM_2.5, PM₁₀, NO₂, SO₂, CO, and O₃ was estimated for each participant from 1994 to 2019. Indoor air quality was determined by ventilation status and daily indoor time. Generalized linear mixed models were used to analyze the association of air pollutants, indoor air quality, and cognition adjusting for important covariates. Over time, per 2.97 μg/m³ (i.e., an interquartile range) increment of PM_2.5 was associated with the poor performance of memory (Z score of a cognitive test, βˆ:-0.14), attention (βˆ:-0.13), and executive function (βˆ:-0.20). Similarly, per 2.05 μg/m³ increase in PM_2.5-10 was associated with poor global cognition [adjusted odds ratio (aOR): 1.48, βˆ:-0.28], attention (βˆ:-0.07), and verbal fluency (βˆ:-0.09); per 4.94 μg/m³ increase in PM₁₀ was associated with poor global cognition (aOR: 1.78; βˆ:-0.37). In contrast, per 2.74 ppb increase in O₃ was associated with better global cognition (βˆ:0.36 to 0.47). These associations became more evident in participants with poor ventilation or short daily indoor time (<12.5 h/day). For global cognition, the exposure to a 10-μg/m³ increment in PM_2.5, PM_2.5-10, and PM₁₀ corresponded to 1.4, 5.8, and 2.8 years of aging, respectively. This study demonstrated how indoor air quality in areas using clean fuels differentially affected the associations of long-term exposure to low-level air pollutants with cognition. Tightening air quality standards may help prevent dementia.

Flow and spillage characteristics of conventional and air-curtain range hoods under static condition were experimentally studied, and their differences in physical mechanisms were compared. Two oil pans containing hot oils heated to 230°C by electric heaters were placed on a countertop to simulate the cooking condition. Large amount of oil fumes were generated and rose from the oil pans. Flow features were examined using laser-light-sheet-assisted oil fume flow visualization method. Local-averaged spillages of tracer gas (sulfur hexafluoride) in the front and lateral planes of the range hoods were detected by employing the tracer-gas concentration detection technique. For the conventional range hood, the flow visualization showed two most probable locations for spillages: the region near the front edge of countertop due to the boundary-layer separation and the region around the lower edge of the hood side panels due to the expansion effect of hot plumes. Detected local-averaged tracer-gas concentrations around these two locations correlated well with the results of flow visualizations. No significant spillages of oil fumes or tracer-gas concentration was observed or detected around the front and lateral planes of the air-curtain range hood. Around the front edge of countertop, the detected tracer-gas concentration of the conventional range hood was larger than that of the air-curtain range hood by about three orders of magnitude. Overall, the air-curtain range hood presented drastically smaller spillages than the conventional range hood.

This mini-review provides the practice guideline recommendations for ventilation of remodeled negative-pressure isolation wards for COVID-19 Patients. Remodeled “quasi-negative-pressure” isolation wards had been proved a feasible, inexpensive, safe, and effective measure to contain nosocomial outbreaks. We should first determine the minimum required ventilation volume of an isolation ward based on the severity of COVID-19 patients. Mechanical ventilation remains the mainstay for achieving the requirement, while the assistance of recirculation is also helpful. Beyond adequate ventilation volume, the “clean to less-clean” directional airflow remains the golden rule for the solution of indoor ventilation. The virus-laden exhaust should be treated with HEPA/UV device or be kept away from living organisms, buildings, and air inlets.

The purpose of this study is to investigate electroosmotic flows driven by externally applied DC and AC electric fields in curved microchannels. For the DC electric driving field, the velocity distribution and secondary flow patterns are investigated in microchannels with various curvature ratios. We use the Dean number to describe the curvature effect of the flow field in DC electric field. The result implies that the effect of curvatures and the strength of the secondary flows become get stronger when the curvature ratio of C/A (where C is the radius of curvature of the microchannel and A is the half-height of rectangular curved tube.) is smaller. For the AC electric field, the velocity distribution and secondary flow patterns are investigated for driving frequencies in the range of 2.0 kHz (Wo=0.71) to 11 kHz (Wo=1.66). The numerical results reveal that the velocity at the center of the microchannel becomes lower at higher frequencies of the AC electric field and the strength of the secondary flow decreases. When the applied frequency exceeds 3.0 kHz (Wo=0.87), vortices are no longer observed at the corners of the microchannel. Therefore, it can be concluded that the secondary flow induced at higher AC electric field frequencies has virtually no effect on the axial flow field in the microchannel.