The American Society for Refrigeration and Air Conditioning Engineers (ASHRAE) has developed an infectious aerosol mitigation protocol and updated it with the latest SARS-CoV-2 mitigation recommendations.
As a faith-based community, consider improving indoor air quality and air movement throughout your facility in accordance with the American Society for Refrigeration and Air Conditioning Engineers (ASHRAE). ASHRAE has developed an infectious aerosol mitigation protocol and updated it with the latest SARS-CoV-2 mitigation recommendations as listed below. The degree to which each solution is applied would be dependent upon the facility type, potential risk and available budget.
-Control temperature and humidity
-Supplying clean air to susceptible occupants
-Diluting the air in a space with cleaner air from outdoors and/or filtering the air
-Cleaning/Sterilizing the air within the room
-Containing contaminated air and/or exhausting to outdoors
Solutions to achieve these building infectious aerosol mitigation recommendations are discussed below.
CONSIDER INTEGRATING UV LIGHT
UV light has three wavelength categories: UV-A, UV-B, and UV-C. UV-C light is a short-wavelength, ultraviolet light that breaks apart virus DNA, leaving it unable to function or reproduce.
a. UV-C inactivates microorganisms by damaging the structure of nucleic acids and proteins with the effectiveness dependent upon the UV dose and the susceptibility of the microorganism.
b. Germicidal UV-C can neutralize 90% or more of all microorganisms in air depending on the lamp intensity and the length of organism exposure time.
c. Avoid extended human exposure to direct UV-C.
d. Practical applications include UV-C airstream array packages with lamps spaced at close intervals can providing airstream disinfection, wall mounted, in room stand-alone UV-C package mounted high, UV-C downlights to disinfect countertop surfaces, 2×4 Troffer LED fixtures with an integral HEPA filter and UV-C airstream disinfecting light, and UV sterilization cabinets to disinfect masks, PPE and other susceptible small components.
AS AN ADDITION OR ALTERNATIVE TO UV-C, CONSIDER BIPOLAR IONIZATION TECHNOLOGY
a. Assembly includes a tube with two or more electrodes. When an Alternating Current (AC) voltage is applied to the tube electrodes, an ionization field of oppositely charged particles is generated around the tube.
b. In the space, oppositely charged ions attract to other micro-particles such as dust, VOC, bacteria and viruses. As ions surround these micro-particles, particles become bigger and heavier by a process called agglomeration. These bigger heavier particles may either fall out of the air due to their weight or could now be more easily captured by HVAC system filters, increasing filter efficiency.
c. Once ions are adhered to the mold, virus, bacteria and dirt particle surfaces, a chemical reaction occurs on the cell membrane surface, and the ions are transformed into OH radicals, which due to their instability, rob the harmful substance of a hydrogen atom (H). The result is that virus particles are inactivated by severing the protein on cell membrane, thusly removing the protective protein layer of the micro-particle and leaving a virus DNA/RNA susceptible to destruction.
d. This technology has been tested in 3rd party laboratories successfully against SARS, MERS, surrogate viruses to SARS-CoV-2 (virus with similar composition) and other coronaviruses.
e. Practical applications include in duct or in air handler bi-polar ionization units. In this instance, the HVAC unit fan distributes the ions into the space through the ductwork and stand alone, mobile plasma generators which could be used in denser, occupied spaces. This technology is similar to bi-polar ionization where electrons, ions and radicals are generated in the filter unit. Air passes through the stand-alone unit and the bacteria and viruses are damaged or destroyed in the filter unit.
CONSIDER HIGHER EFFICIENCY FILTERS IN HVAC SYSTEMS
a. ASHRAE Standard 52.5 provide a standard particulate filter rating system called the Minimum Efficiency Reporting Value (MERV) from which most manufacturers use to rate their filters. MERV 9-12 filters are ideal for dust particulate, MERV 13–16 filters are ideal for airborne bacteria and MERV 17-20 filters (HEPA filters) are ideal for particles 0.3pm or smaller including airborne virus particulate.
b. Most HVAC systems cannot handle the pressure drop of a HEPA filter but MERV 13-16 filters could potentially be leveraged when coupled with bi-polar ionization technology to help increase the size of the airborne bacteria and virus particulate so lower efficiency filters can capture this.
c. The primary intent with higher efficiency air filter systems is to dilute the space by removing micro-particles and giving occupants immune system a boost with cleaner air.
d. Practical applications include one for one 2×2 diffuser replacement with a 2×2 diffuser-HEPA-fan assembly that provides HEPA level (surgical suite level) filtration for all the air delivered from that diffuser, higher efficiency filters in the air handling unit, stand-along HEPA filtration room units, electrostatic air filters which induce a charge on micro-particles passing through the filter and are collected by an oppositely charge collector surface.
CONSIDER ADJUSTING AIRFLOW PATTERNS IN THE BUILDING
This process starts by assessing a new or existing building in a similar manner to how a new hospital would be designed to mitigate transmission of infectious aerosols. Strategy involves defining clean, less clean, and dirty spaces within the building.
a. Clean spaces could be considered communicating corridors and large atrium spaces. Less clean spaces could be considered connecting office suites, classrooms and residence rooms. Dirty spaces could be considered restrooms, janitor’s closets, etc.
b. Clean spaces would potentially have a higher room pressure than less clean spaces and dirty spaces may be under negative pressure through exhaust systems. These pressure differences help prevent room air from less clean spaces from exfiltrating into clean spaces and so on.
c. To implement these pressure differences, the building pressures could be adjusted in numerous ways. Solutions should be handled with care under the supervision of a qualified engineer or technician who understands the building characteristics and capacity of the systems in play. Some potential solutions include fully or partially blocking an air return inlet in clean rooms, increasing ventilation in clean rooms and decreasing ventilation in less clean rooms, adding exhaust in dirty rooms or less clean rooms.
CONSIDER ADDING WATER FILTRATION, ESPECIALLY AT POINTS OF USE CONSUMED BY OCCUPANTS WHO COULD POTENTIALLY BE IMMUNOCOMPROMISED
After conducting an initial water test, a water filtration plan is devised based on the specific contaminants that exceed a designated baseline level.
The Well Building Institute provides specific guidelines on water quality for human consumption that can assist in the determination of appropriate water quality.
These guidelines focus on dissolved metal content, organic pollutants, herbicides and pesticides, fertilizers, disinfectants, disinfectant byproducts, and fluoride.
