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“Transmission of SARS-CoV-2 through the air is sufficiently likely that airborne exposure to the virus should be controlled. Changes to building operations, including the operation of heating, ventilating, and air-conditioning systems (HVAC), can reduce airborne exposures.”


Transmission of SARS-CoV-2 through the air is sufficiently likely that airborne exposure to the virus should be controlled.


Fortunately, HVAC improvements can be made to reduce transmission of airborne microbes in all building occupancy types.


So where do we start to ensure the air we breathe in our buildings is clean?


This is the first of three articles that will address top level strategies to reduce hazardous microbes within buildings. Our topics include:


1. Design strategies to reduce exposure from hazardous airborne microbes.


2. Air purification equipment options, design and potential issues with improper equipment.


3. Testing methods to validate outcomes for peace of mind.


Conduct a Facility Review Schedule an assessment by a professional engineer familiar with industry guidelines and infection control. Whether considering revisions to building HVAC systems or the addition of supplementary air purification equipment, each building is unique and should be inspected to maximize quantifiable outcomes. The report should confirm existing equipment and control adequacy, provide well defined strategies supported by industry guidelines, and provide potential energy and maintenance cost impacts.


The list below includes a summary of the recommended strategies for facility review:


` Dilution Ventilation When possible, increase the outside air volume and increase the air changes per hour (ACH). Fresh air will assist in the flushing and dilution of airborne microbes within the space. A typical office building may range between one to more than six air changes per hour. The engineer will provide information on the ACH


required based on building type and the existing HVAC equipment design capability. Adjustments to HVAC ventilation run times may also be recommended to maximize ACH delivery.


` Filtration Upgrade HVAC filters to MERV 13 or higher rating to improve microbe capture. Confirm that the HVAC equipment can accommodate the higher air flow resistance with these filters prior to upgrading. Wall- mounted ductless fan systems should be evaluated carefully, prior to filter upgrades due to limited capability to handle increased air flow resistance.


` Self-Contained Air Purification Equipment Modular or portable HEPA fan/filter units may be installed to recirculate and purify air within rooms or conference spaces. Dirty air is collected, filtered, made clean and directly returned to the space. There are practical equipment options incorporating both HEPA filtration and UV-C germicidal lighting or needlepoint bipolar ionization. Safety and efficacy considerations should be confirmed prior to selecting equipment. We will discuss the details of equipment in the next article.


` Temperature and Humidity Some research indicates, but is not conclusive, that a virus does not thrive or transmit well when humidity is between 40% and 60%. At the time of this writing, ASHRAE has not taken a definitive position on what temperature and humidity levels to maintain for airborne infection control. Humidity adjustment approaches should be confirmed by a professional engineer to minimize potential negative effects such as microbial propagation (mold).


` Exhaust Increase the operation of the exhaust systems in bathrooms and janitor closets to aid in removing particulate matter. Exhaust operation will draw the air negative and reduce microbe transmission to adjacent spaces.


Next In Series


The next article will address rapidly evolving equipment strategies. We will focus on the details and safety considerations of equipment such as: ` UV-C / UVGI Ultraviolet Germicidal Irradiation ` Needlepoint Bipolar Ionization (NPBI) ` HEPA Filtration ` Self-Contained Air Purification Equipment ` Fog Sterilization


There are a variety of design considerations and it is important that you are getting the best information available; don’t fall for gimmicks. Proper evaluation and planning with a qualified company will protect you and your community through these difficult times.


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