EI Associates is assisting several NJ Public School Districts with the evaluation of mechanical systems relative to COVID19 indoor air quality concerns. There is no single recommendation for improving indoor air quality regarding COVID19. The following basic recommendations are intended to help reduce the spread of infection:
- Increase outside air
- Better filtration, minimum MERV 13 filters and more frequent filter changes
Reliance on outside air natural ventilation is not practical during inclement weather. Natural ventilation systems rely on pressure differences to move fresh air through buildings. Openings between rooms such as transom windows, louvers and grilles facilitate air-flow through buildings. Code requirements regarding smoke and fire present challenges to natural ventilation systems. Some spaces do not have the required amount of operable window area. Ideally all spaces would be renovated to provide reliable year round mechanical ventilation with proper air treatment filtration and conditioning.
For the near future when the weather is warm, AC should not be used even if it is available. Unit Ventilators (UVs) (at least reasonably modern ones) are equipped with an enthalpy cycle which shifts the unit to 100% outside air automatically when outside air is cooler than inside. This should be utilized until the weather gets very cold. UVs can be set to run longer in this cycle at the expense of increased heating costs.
For filtration, install MERV 13 filters for unit ventilators at a minimum. MERV 13 is a considerable upgrade over MERV 4 (blue) filters typically used. MERV 13 filters are effective at capturing Droplet Nuclei particles (from a sneeze) but not an unattached virus. For unattached virus a MERV 17 filter is required. Unfortunately, due to the large static pressure and thickness, MERV 17 filters are not suitable to retrofit in most existing HVAC equipment. The downside is MERV 13 filters need to be replaced often, especially when pollen is present.
Global Plasma Solutions (GPS) has a system called Needlepoint Bipolar Ionization that we have specified for several installations. Through the involvement of the Federal Government, this system was recently tested for use against COVID19 and results have been published (this test was requested by the FAA for a simulation that would be found in an airplane cabin). The GPS system ionizers operate at a power level just below what would create ozone and is safe for use in educational settings. The system is relatively easy and inexpensive to install in most HVAC equipment and causes particles to agglomerate into larger ones so it enhances the filters ability for capture.
EI Associate does not believe there is any down side to the installation of these systems. They will not damage UVs or other mechanical equipment. They have been used in NJ schools by ESIP companies for years to reduce code required fresh air requirements and provide related energy savings. Once this pandemic is over, units provided with ionizers can be adjusted to reduce outside air thereby reducing energy consumption and operational costs. For now, more outside air is reported to be helpful.
Another consideration is to provide for isolation and negative pressure rooms within or in close proximity to the Health Services Areas for anyone deemed infected while inside the school.
Districts should assure that all mechanical equipment is in good repair and properly functioning. Filters should be changed regularly. Outside air dampers should be set to provide the maximum outside air within the constraints of the weather conditions. Operable windows should be fully functional and utilized as much as possible. Spaces without mechanical ventilation should not be occupied during the current COVID19 pandemic until HVAC systems with code compliant mechanical ventilation systems can be added.
Portable air purification systems can be utilized as a temporary measure. Systems are available with options for UV light sterilization and bi-polar ionization.
Please note the above considerations are in addition to, not a substitution for, the recommendations of the CDC such as social distancing, face covering and hand washing.
Our in-house team of mechanical engineers is available to review your needs, provide recommendations and share our 76 years of K-12 public school ventilation system experience.