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How will PPS maintain good indoor air quality and mitigate transmission of COVID-19?

To provide good air quality, PPS uses filtering methods to reduce particles, odors, and micro-organisms including mold, bacteria and virus particles. PPS has focused on the primary components of clean air which include dilution (air exchange and the inclusion of fresh air); exhaust; and humidity control.

  • The district has installed Airedale Classmate units equipped with Needlepoint Bipolar Ionization (NPBI) and MERV-13 filters in all classrooms in Princeton Middle School, Community Park, Johnson Park, Littlebrook and Riverside. These units deliver 6 to 8 air changes per hour and a minimum of 30 percent of outside air. Most classrooms have a 3 or 4 ton unit that is circulating and filtering 1100 and 1500 Cfm (Cubic Ft / minute) respectively.
  • In Princeton High School the District has installed NPBI, the goal of which is to have the MERV-8 filters to function as effectively as MERV-13 filters. The HVAC system at PHS is not designed to handle MERV-13 filters. 
  • The Airedale units achieve dilution through their capacity to move more outside air (up to 100 percent when low humidity and moderate temperatures exist).
  • The Airedale units are also equipped with CO2 monitors.
  • Humidity is monitored and maintained at 55-60 percent.
  • The intent of installing NPBI is to increase the size of particulate matter, through the process of agglomeration. This allows our filters to trap more particulate matter.
  • PPS decided to implement NPBI from Global Plasma Solutions, last summer, based on studies that showed promising efficacy. The NPBI technology has been widely adopted in the airline industry with seemingly positive results to date. Universities and many other school districts have also opted for this technology which is just one part of the strategy.
  • As recommended by our health and safety experts, PPS has installed commercial grade air purifiers with HEPA filters in the nurse's offices in all six schools. We have also outfitted the HVAC units that provide ventilation in the nurse's stations across the district with NPBI, as well as making sure the units are 100 percent operational.

Describe the HVAC situation at Princeton High School.
Princeton High School has unit ventilators that provide heating and air conditioning and to each classroom. The Facilities Department did a comprehensive operational check last year (and again this year), including the outside air damper function and controls. The unit ventilators deliver close to 20 percent outside air, providing approximately 8 to 8.5 air changes per hour.

Is the District considering purchasing additional portable HEPA air purifiers?
We will examine the possibility of using federal American Rescue Plan education funds to purchase additional portable HEPA air filtration units for broader use of this technology in our schools.

Have there been additional ​indoor air quality measures implemented to reduce the spread of COVID-19 in PPS schools?
In addition to increasing outside air percentage, the NPBI technology in all the Airedale units, PPS has installed NPBI in key rooftop HVAC units.

What technology does PPS use to monitor indoor air quality?
The monitoring takes place in each individual classroom using the Airedale equipment's self-monitoring and alert capabilities.

Describe other recent improvements in school ventilation.

  • Several things were done district wide last year related to ventilation that improved air quality, including overriding energy saving devices, occupancy sensors, and CO2 sensors that normally reduce ventilation. PPS increased ventilation of outside air levels as much as possible without compromising the room temperature, and most importantly, without increasing the humidity level.
  • With the level of mechanical ventilation provided by the new Airedale units, we are able to limit reliance on opening windows for proper ventilation. If we generally keep the classroom windows closed, we can let the HVAC dehumidify, filter the air, and bring in outside air while tempering and reducing the outside air humidity level.
  • This will help provide the safest environment that we can with respect to humidity factors impacting viral transmission.
  • Additionally, by keeping windows closed we can control the direction of airflow so it travels along the ceiling and drops to the floor, rather than blowing across the room and passing by each students breathing zone at the open window level.


NJ Department of Health: The Road Forward

NJ Department of Health
Maintaining Healthy Indoor Air Quality in Public School Buildings

CDC: Ventilation in Buildings Guidelines

CDC: Guidance for Schools




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