An investigation of thermal environment of an existing UFAD system in a high-rise office building in the tropics

Odour and indoor air quality hazards in railway cars: an Australian mixed methods case study

Purpose

This case study aimed to diagnose the cause(s) of a seasonal, and objectionable odour reported by travellers and drivers in the railway cars of Australian passenger trains. The research questions were to: (1) identify whether significant microbial colonisation was present within the air handling system of trains and causing the odours; to (2) identify other potential sources and; (3) remedial options for addressing the issue.

Methods

A mixed-methods, action research design was used adopted. Sections of the heating, ventilation, and air conditioning (HVAC) systems from odour-affected trains were swabbed for bacteria and fungi and examined for evidence of wear, fatigue and damage on-site and off-site. Insulation foam material extracted from the walls of affected trains was also subjected to a chemical assessment following exposure to varying humidity and temperature conditions in a climate simulator. This was accompanied by a qualitative sensory characterisation.

Results

Upon exposure to a variety of simulated temperature and humidity combinations to recreate the odour, volatile chemical compounds released from the insulation foam by water were identified as its likely cause. In addition, a range of potentially serious pathogenic and odour-causing microbes were cultured from the HVAC systems, although it is considered unlikely that bacterial colonies were the odour source.

Conclusion

The research has implications for the sanitising and maintenance policies for HVAC systems on public transport, especially when operating in humid environments. The sanitary imposition, especially in the wake of COVID-19 may be required to ensure the safety of the travelling public and drivers.

A systematic review of ventilation conditions and airborne particulate matter levels in urban offices

Many working activities are carried out in office buildings that are located in urban areas. Several studies have shown that these workplaces are likely to present poor indoor environmental quality (IEQ) due to inadequate ventilation rates, compromised thermal comfort conditions, and/or high concentration of air pollutants, such as particulate matter. This study aimed to review ventilation conditions, based on carbon dioxide (CO₂ ) concentrations, and indoor airborne particulate matter (PM_2.5 and PM₁₀ ) levels assessed in offices worldwide. The approach carried out in this work followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Six databases (Scopus, Web of Science, PubMed, Inspec, Science Direct, and Dimensions) were used to search for peer-reviewed articles on the subject of IEQ, in particular, those reporting data for the levels of CO₂ and particulate matter in offices, published during the last decade. Firstly, 394 records were identified, resulting in 23 articles included in the review after the screening process and the implementation of eligibility criteria. Based on the results and considering the mean concentration reported, office environments present, in general, acceptable ventilation conditions (mean: 665 ppm). However, the few cases of studies that reported CO₂ values exceeding 1000 ppm identified situations of high occupancy density and inadequate operation of heating, ventilation, and air conditioning (HVAC) systems as the unequivocal causative factors. In turn, PM_2.5 and PM₁₀ seemed to be IEQ parameters that are even more critical to be tackled in offices, with the reported overall mean values (36 and 63 μg/m³ ) exceeding the current World Health Organization (WHO) guidelines (15 and 45 μg/m³ ). The highest aerosol concentrations were typically found in naturally ventilated buildings and were mostly associated with the influence of high levels of particles introduced indoors through the outdoor air. Overall, measures for improving IEQ in offices toward promoting healthy and safe environments for workers include strategies to periodically control IEQ, ensure the adequate percentage of fresh air and maintenance of the mechanical ventilation systems (operation, maintenance, and air filtration efficiency), and adjust occupancy to the room dimensions and ventilation conditions.

Effects of Air Supply Terminal Devices on the Performance of Variable Refrigerant Flow Integrated Stratum Ventilation System: An Experimental Study

A variable refrigerant flow integrated stratum ventilation (VRF-SV) system was proposed as an energy efficient substitute for conventional central cooling systems for buildings. The novel system provided conditioned air to enclosed spaces with high indoor air quality and thermal comfort. This study investigated the effects of different types of ASTDs on the performance of the VRF-SV hybrid system. The performance was experimentally evaluated with five air terminal types, including bar grille, double deflection grille, jet slot, perforated and drum louver diffusers. The evaluation was carried out using standard indices: temperature and velocity distribution, airflow pattern, effective draft temperature (EDT), air distribution performance index (ADPI), thermal sensation vote and comfort feedback survey. The results indicated that the ASTD type had a significant impact on airflow pattern. Furthermore, the bar grille diffuser provided the occupants with greater thermal comfort and acceptable indoor environment. Almost all the EDT values determined in the breathing zone in the case with bar grille diffuser found under the satisfactory range, i.e., −1.2 < K < 1.2. Based on these values, the ADPI for bar grille diffuser was calculated as 92.8%. Thus, the bar grille diffuser is recommended to be installed with the VRF-SV hybrid system in buildings.

Numerical simulation of airflow and particle distributions with floor circular swirl diffuser for underfloor air distribution system in an office environment

In the present study, an underfloor air distribution (UFAD) system with a circular swirl diffuser was simulated in an office room using a three-dimensional model when thermal sources were present in the room. An Eulerian-Lagrangian model was used to predict the characteristics of air and particle phases. In the Lagrangian particle model, the effects of drag, lift, Brownian, and thermophoresis forces were considered. The results showed that the circular swirl diffuser has better airflow and thermal conditions compared with the circular direct diffusers. It was also shown that the studied UFAD system provides good thermal comfort condition. The local and mean normalized particle concentrations in different heights of the room were found reasonable, and the particle removal efficiency was between 55 and 65% for all the particle sizes. The results also showed that the large particles due to their large weight stayed in lower heights of the room and deposited on the floor. The particle concentration in the breathing zone of manikins was also investigated, and it showed that though the manikins seated close to inlet registers have appropriate thermal comfort, they encounter the highest particle concentration in their breathing zone.