Conference Agenda

TiO2-based photocatalytic oxidation process (PCO) is an environment-friendly and promising air purification technology for degrading indoor air volatile organic compounds (VOCs) at ambient temperature and pressure. However, several significant limitations, such as low photoactivity under visible light irradiation, a high rate of charge carrier recombination, limited adsorption capacity, and the formation of hazardous by-products, have hindered the commercialization of this technology. In this study, synthesized TiO2 was coupled with another semiconductor (WO3) at varying W/Ti molar ratios to address some of its limitations for removing methyl ethyl ketone (MEK) as a model pollutant from the indoor air environment. The synthesized photocatalysts were coated onto nickel foam, and their photocatalytic performance, along with the identification and quantification of gaseous by-products formed, was evaluated in a continuous-flow reactor with a short residence time, and an inlet concentration of 2.5 mg/m3, and 40% relative humidity (RH). The physicochemical properties of the prepared photocatalysts were characterized by XRD, SEM, N2 adsorption-desorption, DRS, and PL. The results showed that coupling TiO2 with WO3 extends its spectral response into the visible light range, with a significant improvement in visible-light-driven photocatalytic activity demonstrated for 3%WO3-TiO2 (3%WT) compared to bare TiO2. Specifically, the removal efficiency increased from 32% to 61% under visible light irradiation. Also, the formation of identified by-products (formaldehyde, acetaldehyde, and acetone) was significantly reduced when TiO2 was coupled with WO3, compared to pure TiO2.

Semi-Volatile Organic Compounds (SVOCs) are indoor air pollutants with significant potential health concerns, yet they have not received sufficient attention within the ASHRAE community. Phthalate Esters (PAEs), a subgroup of SVOCs, have been widely used as plasticizers in consumer products and building materials for over a century. Due to their low vapor pressure, phthalates readily partition onto surfaces, including ubiquitous particulate matter, which serves as a vector for human exposure. Understanding the behavior of phthalates in indoor air necessitates the development of methods to generate stable and controlled gas-phase emissions. This study explores the relationship between temperature and gas-phase generation of phthalates under controlled laboratory conditions. Current state-of-the-art methods for generating phthalates include (1) using building materials, such as PVC, as emission sources, (2) utilizing pure liquid phthalates, and (3) embedding phthalates into porous media. For this study, pure di-n-butyl phthalate (DnBP) was embedded in a fibrous glass medium housed within a stainless-steel tube, selected for its thermal stability. Gas phase concentrations were controlled by the temperature of the media. Experimental results demonstrate that temperature significantly influences DnBP gas-phase concentration. At 19°C, the concentration measured 60 µg/m³, increasing to 182 µg/m³ at 38°C. A further rise to 57°C caused a dramatic increase to 13,062 µg/m³. These findings highlight the role of temperature in phthalate emissions and provide insights for better understanding their partitioning behavior and exposure risks in indoor environments.

The application of plant-based phytoremediation in indoor air quality management has garnered increasing attention in recent years. Compared to traditional indoor mechanical ventilation and physical filtration systems, these green biofiltration facilities offer greater sustainability and unique advantages. Studies have established that air purification involves not only the aboveground parts of plants but also plant roots and their associated soil microorganisms, which play a crucial role in the breakdown and metabolism of pollutants. The term rhizoremediation is used to describe this remediation process, which has been extensively studied in the fields of water and soil pollution. However, the response of rhizospheric microorganisms to airborne pollutants remains largely unexamined. In the context of air pollution, volatile organic compounds (VOCs) such as benzene, toluene, ethylbenzene, and xylene (BTEX) are widely recognized as key indicators for pollutant monitoring. While most studies to date have focused on the phytoremediation of individual pollutants, air pollutants in real-world environments typically exist as complex mixtures. To address this limitation, this research used gasoline vapours to simulate real-life mixed air pollution sources. In sealed experimental chambers, rhizospheric microbial community dynamics will be compared with and without plants to identify microbial groups involved in air pollutant degradation. The study employed 16S rRNA gene sequencing to identify bacterial species and qPCR to track changes in the relative concentrations of four enzymes specifically associated with BTEX degradation. The findings aimed to uncover the collaborative mechanisms of plants and rhizospheric microorganisms in the degradation of air pollutants. Additionally, the study emphasized the essential role of microorganisms in bioremediation and their synergistic interactions with plants to enhance air purification.

Indoor air technologies are not optimized for health, speed, and scale. The binding constraint to this ecosystem is the technical and commercial immaturity of sensor technology, which is currently unable to accurately, rapidly, and cost effectively detect biological pathogenic contaminants. This limitation greatly hinders the advancement and commercialization of downstream risk assessment and building control technologies by preventing a timely, effective response between pathogen detection and mitigation. Moreover, it perpetuates an industry paradigm to design and operate buildings around ventilation rates, carbon dioxide levels, and proxy metrics that can be highly inaccurate and misleading for pathogen control, with negative consequences for capital and operating expenditures and energy efficiency.

First, our paper will describe current limitations for sensors, risk assessment, and building controls:

• Sensors: focus on chemical and particle detection, with pathogens requiring manual intervention; time-lagged results arrive too late to respond to threats; and there are no market acceptable options for airborne pathogen detection currently available

• Risk assessment: lacks standardized measurement for air biology, with health and building risk not well-integrated; is characterized by infrequent, point-in-time assessments; and is service not product-driven and human not software-driven

• Building controls: are optimized for thermal comfort and cost, with an inability to correlate controls to health outcomes or risks; automation is limited to CO2 demand-controlled ventilation for health; and there is a limited ability to automate and limited scope of controls

Second, we will describe a technology platform consisting of biosensor technology for real-time detection of airborne pathogens integrated with rapid, automated, and risk-informed building controls targeted to building- and pathogen-specific interventions to detected pathogens.

Third, we will discuss key considerations for real-world deployment and scaling of this integrated technology platform including: 1) priority building categories; 2) return on investment quantified in a triple bottom line methodology; 3) integration with ASHRAE Standard 241.