+ What was the purpose of the Well Living Lab’s Classroom Air Purification Study?

Our Classroom Air Purification Study examined how portable air purification units may reduce the travel and surface deposition of airborne particles, both near the units and throughout the whole room. The results suggest portable air purification units might mitigate the transmission of respiratory viruses such as COVID-19 in a classroom space but can also be applied to similar sized spaces.

+ What was the goal of the study?

The goal of the study was to provide guidance on proper placement of portable air purification units in classroom settings to help schools improve student health. Based on the findings of this study, school administrators and decision-makers may choose to invest in portable air purification units as part of their effort to create a safer learning environment – a cost-effective alternative to renovating an HVAC system.

+ What methods did the Well Living Lab use to conduct this research?

The Well Living Lab was designed to be highly reconfigurable, so to conduct this research, we converted our office research module into a 900-square foot simulated classroom, complete with strategically positioned classroom furniture such as student and teacher desks/chairs, whiteboards, computers, and iPads.

We connected a breathing simulator to an anatomically correct manikin to mimic the inhalation and exhalation of a 5’3”108-pound female. The simulator exhaled particles injected with a fluorescent dye and similar in size to that often tied to transmission of airborne infectious disease transmission. The dye allowed us to measure how many particles landed on surfaces throughout the classroom as well as the number of particles present in the air.

+ What were the findings from the study?

Compared to our Baseline Condition using only the room’s HVAC system:

• We observed a localized impact of portable air purification units on the number of aerosol particles present in the air, with the air nearest these units often freer of aerosol particles (i.e., a lower number of aerosol particles in the air) than at distances further from the unit.
  • This was particularly true when the portable air purification units were positioned closer to the infectious source. This would have the effect of limiting the potential for direct inhalation of particles in the air.
• We observed the speed that aerosol particles deposited in the classroom to be slower when using the portable air purification units’ full functionality, likely due to the capture of these particles within the filters of the units.
  • This would have the effect of limiting potential exposure to deposited particles on surfaces.
• We observed speedier removal of aerosol particles from the entire classroom following each study condition where portable air purification units were present.
• We determined the number of air changes per hour (ACH) increased to around 6 ACH when running the three air purification units – a notable increase from the Baseline HVAC-only value of 3.4 ACH. This aligns with the 4-6 ACH recommendations for classrooms from Harvard, Johns Hopkins, CDC, and others.

+ What type of air purification units were used in the study?

The air purification system used in the study was the Healthway Intellipure Compact.

Product Features and Specs include:

• Coverage - Up to 550 square feet
• System Efficiency – high CFM rate with low energy consumption
• Multiple Fan Speeds – four fan speeds for ease of control
• DFS Filtration Efficiency – 99.99% aggregate removal of particles down to 0.007 micron**
• Independent Air Flow/Distribution Control – to facilitate placement anywhere in the space
• Ease of Maintenance – designed for quick and easy filter maintenance and replacement
• Multiple Configuration - wall mountable or stand-alone installation options
• Fan Speeds Turbo, High, Medium, Low
• Voltage/Frequency 120V/60Hz (High), 220V/50Hz (Medium), 220V/60Hz (Low)

+ How many air purification units were present during the study?

We used three air purification units positioned equidistant throughout the classroom.

+ How many conditions were conducted to obtain your findings?

We conducted four study conditions with two paired experiments per condition over a period of eight weeks. The conditions included one baseline condition with only the classroom HVAC unit running. The three other conditions used baseline HVAC plus the three portable air purification units set to various experimental settings. Each study condition took approximately 1.5 hours, with the preparation, post-processing, measurements, and cleaning taking between 25 and 30 hours per condition.

In each condition, we looked at factors such as:

• The mass concentration of particles that deposited on surfaces throughout the simulated classroom.
• The mass concentration and number of particles present in the air near each portable air purification unit and throughout the classroom.
• Whether the electrostatic impact of electronics increases particle deposition to items, potentially increasing exposure to infectious particles when using these devices.

+ Who were the collaborators for the study?

We collaborated with the University of Minnesota and Mayo Clinic on the Classroom Air Purification Study. Specifically, we worked closely with Dr. Chris Hogan, a Professor in the Department of Mechanical Engineering at the University of Minnesota and editor-in-chief of the Journal of Aerosol Science, and his team. Mayo Clinic Respiratory Care provided the anatomically correct respiratory manikin for use during the study.