Optimizing Elderly Care Bedroom Ventilation and Indoor Air Quality

The research paper by Wu, Kumar, and Cao (2024) addresses the critical challenge of ensuring adequate ventilation and indoor air quality (IAQ) in elderly care centres (ECCs), a pressing concern given the global increase in the elderly population and their heightened susceptibility to air pollutants due to weaker immune systems. Focusing specifically on typical two-bed bedrooms in ECCs, which often house elderly individuals with special needs, including bedridden residents or those requiring caregiver assistance, the study aims to identify effective ventilation design measures. The authors highlight that designing ventilation for ECC bedrooms is distinct from other indoor environments like offices or hospitals, emphasizing the unique characteristics and requirements of elderly residents, particularly the need to balance improved air quality with residents’ privacy and well-being.

The study investigated four primary ventilation types: mixing ventilation (MV), displacement ventilation (DV), zone ventilation (ZV), and stratum ventilation (SV). To comprehensively assess their effectiveness, twelve distinct scenarios were analyzed: six with curtains installed between the beds to provide privacy and six without curtains. The methodology employed Computational Fluid Dynamics (CFD), an essential tool for predicting and evaluating indoor air parameters, alongside experimental studies conducted in an actual elderly care centre in Nanjing, China, for validation. The performance of each ventilation scenario was evaluated based on airflow distribution, CO2 concentration, ventilation efficiency (Contaminant Removal Effectiveness – CRE), and health risk assessment (Hazard Ratio – HR).

Key Findings of the Study:

• Impact of Curtains: While scenarios without curtains between beds showed a slight (≤8%) decrease in CO2 concentration in the pillow area compared to those with curtains, the study strongly recommends installing curtains. This is because removing curtains would increase the risk of virus transmission and compromise the privacy of elderly residents, which is deemed unacceptable despite minor air quality improvements.
• Superiority of Stratum Ventilation (SV): The research consistently found stratum ventilation to be the most effective method for improving air quality in ECC bedrooms.
  • Improved Airflow Distribution: SV significantly enhanced airflow distribution in key occupancy and breathing areas, especially around the pillows, ensuring fresh air delivery directly to the breathing zone. In contrast, MV, DV, and ZV often resulted in air recirculation zones or slow air velocities, leading to inadequate pollutant dilution.
  • Reduced CO2 Concentrations: All proposed SV models achieved CO2 concentrations below the recommended 800 ppm standard for vulnerable groups, a significant improvement over the current ventilation system’s levels which exceeded 1000 ppm. Specifically, Model SV3c (with curtains) and SV3d (without curtains) demonstrated the lowest CO2 levels (approximately 400 ppm for SV3c in the pillow area and 498 ppm for SV3d), largely due to the optimal placement of air outlets near pollution sources.
  • Higher Ventilation Efficiency (CRE): SV significantly improved contaminant removal effectiveness. In scenarios with curtains, SV was 2.58, 3.22, and 2.12 times more efficient than MV, DV, and ZV, respectively. This efficiency was even higher in rooms without curtains. The study highlights that positioning air outlets near the breathing zone (e.g., pillow area) greatly enhanced pollutant removal.
  • Lower Health Risks (HR): Stratum ventilation models exhibited significantly lower hazard ratios (HR < 1.00 for most SV models), indicating reduced health risks for elderly residents. Compared to other ventilation systems, SV decreased health risks by 46.3% to 53.7% with curtains and approximately 38.5% to 58.4% without curtains.

Recommendations and Implications:

Based on these findings, the study provides practical recommendations for ECC managers, building designers, and local governments. It advises ECC managers to implement stratum ventilation systems in two-bed bedrooms, ensuring air outlets are positioned close to each pillow area (breathing zone) and air inlets are on the opposite wall. Furthermore, it underscores the importance of maintaining curtains between beds to uphold the elderly’s privacy and prevent increased virus transmission risk, even if it means a slight compromise on uniform airflow distribution. Designers are encouraged to collaborate with engineers to prevent stagnant air zones and integrate SV systems aesthetically. The study also calls for continued collaboration among environmental engineers, designers, policymakers, and the wider community to foster sustainable indoor environments for the elderly.

This research serves as a valuable guide for systematically designing ventilation systems in ECC bedrooms, emphasizing a holistic approach that prioritizes both air quality and the physical and mental well-being of elderly residents.

Reference: Wu, H.-W., Kumar, P., & Cao, S.-J. (2024). Evaluation of ventilation and indoor air quality inside bedrooms of an elderly care centre. Energy & Buildings, 313, 114245. https://doi.org/10.1016/j.enbuild.2024.114245.