ASHRAE Standard 241 Testing at ARE Labs
May 30, 2024
Introduction
The ongoing global concern over airborne diseases has highlighted the critical need for effective air quality management in public and private spaces. Infectious aerosols are a primary vector for the transmission of respiratory diseases. The COVID-19 pandemic and yearly flu outbreaks underscore the importance of managing these aerosols in indoor environments to prevent widespread health crises.
In response to this need, the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) has developed Standard 241, "Control of Infectious Aerosols." This standard is essential for architects, HVAC engineers, and public health officials aiming to enhance indoor air quality and reduce disease transmission. Many labs cannot perform the biological or chemical aspects of this standard. At ARE Labs, we provide all the testing for ASHRAE Standard 241 under one roof.
Overview of ASHRAE 241
ASHRAE Standard 241 provides guidelines and strategies for mitigating the risk of infectious aerosol transmission in buildings. The standard covers various aspects of building design, operation, and maintenance that contribute to indoor air quality and health safety.
Critical Components of the Testing
Testing Environment: All ASHRAE 241 testing takes place in a state-of-the-art 30m3 sealed testing chamber under strict environmental conditions outlined in the standard.
Testing Species: All ASHRAE 241 biological testing is done with the unenveloped positive sense single-stranded RNA virus MS2 bacteriophage. Formaldehyde, ozone, and particulates are monitored for the safety portion of the standard.
Testing Method Overview
ASHRAE Standard 241 required testing:
MS2 bacteriophage bioaerosol reduction testing
Formaldehyde byproduct formation testing
Ozone byproduct testing according to UL867 guidelines
Particulate testing according to ISO18644-14
Noise production testing
Figure 1: Example plot ASHRAE Standard 241 log-reduction results using for RNA Virus MS2. Triplicate controls and triplicate trials tested in a 30m3 Bioaerosol Chamber.
Calculation of Clean Air Delivery Rate
The Clean Air Delivery Rate (CADR) is a crucial metric in the assessment of air purifiers, particularly in the context of ASHRAE 241 bioaerosol testing. CADR quantifies the volume of filtered air delivered by an air purifier, measured in cubic feet per minute (CFM). This metric reflects the efficiency and effectiveness of an air purifier in removing specific pollutants, including bioaerosols, from indoor air.
Figure 2: Method for Calculating the Clean Air Delivery Rate using Viral concentrations (pfu/Liter air) obtained during sampling per ASHRAE Standard 241 standard. The difference in the slope for the control (natural decay) and the device trial is used to calculate the devices effectiveness (CADR).
The base calculation of CADR involves measuring the airflow rate and the percentage of particles removed from the air. Essentially, a higher CADR indicates a more effective air purifier. Consumers can use CADR to compare different models by looking at the ratings for various pollutants, allowing for informed decisions based on the purifier's ability to handle the specific contaminants present in their environment. By standardizing these comparisons, CADR helps ensure that air purifiers meet specific performance benchmarks, enhancing indoor air quality.
Figure 3: Table Showing the Clean Air Delivery Rate for this particular device tested in accordance with ASHRAE 241 standard.
Implications for Public Health and Building Design
Implementing ASHRAE 241 can positively impact public health by reducing the incidence of airborne diseases. For architects and builders, this standard provides a framework for designing healthier buildings better equipped to control the spread of infections.
Future Directions
As research on infectious aerosols continues, ASHRAE Standard 241 will likely undergo updates and refinements. Future revisions may incorporate emerging technologies and new scientific insights, further enhancing our ability to manage airborne pathogens. ARE Labs is prepared to adapt to any changes to the standard that may occur later.
References and Further Reading
If you are interested in ASHRAE 241 testing or need more detailed information regarding the testing standard, contact ARE Labs today.
