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Considering the valuable lessons learned during the pandemic, the role of building engineering controls in reducing the spread of infection has become increasingly important. Ventilation, filtration, and air cleaning are key factors in improving indoor air quality during times of heightened infection risk.

The introduction of ASHRAE Standard 241, "Control of Infectious Aerosols," marks a pivotal moment in providing clear guidance for improved indoor air quality to help control the spread of infection. This standard not only underscores the critical importance of managing infectious aerosols but also provides a comprehensive framework for the application, efficacy, and safety of electric air cleaners in various settings.

The Genesis of ASHRAE Standard 241

Developed in response to the need for enhanced indoor air quality standards during increased time of infection risk, ASHRAE Standard 241 provides much needed guidance on strategies to improve the reduction of infectious material in indoor air. It offers detailed design considerations, product qualification requirements, and robust guidelines for owners, architects, engineers, and contractors aiming to effectively mitigate the risk of infectious aerosol transmission. The goal is clear: to ensure the safe and efficient delivery of clean air in indoor environments.

Key Features of the Standard

ASHRAE Standard 241 introduces several key features designed to elevate indoor air quality standards, including:

  1. Compliance with Existing Ventilation Standards: HVAC systems must meet the requirements of ASHRAE 62.1, 62.2, or 170, ensuring adequate minimum ventilation rates.
  2. Independent Testing of Air Cleaners: To guarantee effectiveness and safety, air cleaners must undergo rigorous testing by independent third-party laboratories.
  3. Equivalent Clean Air (ECAi) Calculation: a new method to calculate all the benefits provided by air cleaners, recirculated and filtered air and ventilation in a space.
  4. VACS: an innovative approach to account for the effectiveness of an air cleaner and scale its laboratory performance to real-world spaces, providing a standardized approach to evaluating air cleaner performance.
  5. Pathogen Removal Efficiency: filters, considered as part of air cleaning systems, are required to meet specific efficiency criteria for pathogen removal.
  6. ECAi Compliance Calculator: a handy tool included in the standard assists in evaluating compliance with ECAi requirements for different spaces, streamlining the process for professionals.

Evaluating Air Cleaners

The evaluation process for air cleaners involves thorough testing for both effectiveness in inactivating infectious aerosols and safety of the air cleaner product. Independent third-party labs conduct standardized procedures to ensure unbiased results, covering aspects such as chamber conditions, equipment used, noise levels, electromagnetic radiation levels, and overall test outcomes. Furthermore, the standard mandates safety testing to comply with limits for ozone emission, formaldehyde generation, and airborne particle concentration.

Beyond Traditional Ventilation: VRP vs. ECAi

ASHRAE Standard 241 upgrades the traditional Ventilation Rate Procedure (VRP) outlined in ASHRAE 62.1, which primarily focuses on contaminant dilution. The standard argues that VRP alone is insufficient for managing infectious particles, introducing the ECAi as a more effective measure that necessitates additional controls beyond minimum ventilation. Factors such as cost, system capabilities, and complexity play a crucial role in achieving equivalent clean air, highlighting the significance of air cleaners, filters, and other strategies in meeting ECAi requirements.

Conclusion: Paving the Way for Cleaner Air

The introduction of ASHRAE Standard 241 represents a significant milestone in the pursuit of healthier indoor air quality and the control of infectious aerosols. By providing a standardized approach for the evaluation and application of air cleaners, this standard lays the groundwork for more professional, scientific compliance. As the standard continues to evolve, it promises to play a central role in shaping the future of indoor air quality management, with air cleaners expected to become increasingly prevalent in the pursuit of clean air. In this new era, ASHRAE Standard 241 stands as an industry-accepted guidepost, steering us toward healthier indoor environments for all.