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Preventing infections inside the building means carefully designing and monitoring ventilation and air filtration systems, as well as performing regular maintenance on a building’s water system.
The design of ventilation and air distribution systems is essential to minimize the spread of infectious diseases as buildings continue to reopen. Improving indoor air quality (IAQ) has been a priority for managers as the pandemic continues.
The following checks and potential changes will serve to minimize the spread of any airborne pathogens:
Checking the ventilation: The ASHRAE recommends that all installations follow ANSI / ASHRAE 62 in order to provide acceptable IAQ for human occupants and to minimize adverse health effects. Compliance verification can be carried out as part of a technical inspection or during a retrocommissioning.
Ventilation optimization: Increasing the amount of fresh air beyond the rates required by ANSI / ASHRAE 62 is one of the major modifications that many buildings adopt to minimize the spread of aerosols from airborne infections. However, an increase in ventilation air will result in increased energy consumption to heat and cool the fresh air brought into the building. This increased demand may be a reason to re-evaluate the heating and cooling capacity and operation of installed equipment.
Increased filtration: Another action managers can take is to increase the level of filtration in existing HVAC systems. Filtration of outdoor air can not only mitigate the transmission of infectious aerosols, but can also be used to protect occupants during wildfire season, a major problem in many parts of the country. Similar to increasing ventilation air, this measure can lead to an increase in the building’s energy consumption. Existing air handling units will also need to be evaluated to determine if additional filtration will fit existing cabinets.
Ultraviolet germicidal irradiation can also be added to existing central air distribution systems as a method of mitigation. It will not affect the flow of air or water in the building.
Increased hours of operation for flushing buildings – running air handling units and terminals before tenants arrive and after they leave, will help flush the building and minimize pathogens suspended in the building. air.
Water system maintenance
A building’s water supply system is one of the most likely locations for Legionella growth and for scaling / leaching potential. When reopening buildings, managers should take the following steps to minimize risk.
First, flush all service lines, hot water lines, and cold water lines. Run water through all points of use such as showers, faucets, toilets, potable water, dishwashers and refrigerators / ice makers.
It is also important to drain all water heaters and tanks. Clean and maintain all fixtures in the plumbing system according to the manufacturer’s instructions.
Consider doing a high temperature rinse as a Legionella mitigation measure by refilling the system and then rechecking the water quality. If the water quality is not within acceptable parameters after flushing and filling the system, it may be necessary to flush the system with chlorine or another disinfectant.
After taking these initial steps, it is important to continue ongoing maintenance by taking the following steps.
- Make sure the hot water is stored at 140 degrees to minimize the risk of Legionella in the central system.
- Check the temperature of the mixed water at the outlet of the central mixing valve.
- Make sure that the domestic water recirculation pump is running periodically to minimize stagnation of the hot water system.
Identifying and managing hazards in existing buildings is essential for the safety of building occupants after the pandemic. The above recommendations provide a starting point for ensuring a safe and productive return to the new normal as the world moves forward.
Patrick Strobridge, CPD, Director, Mechanical Engineering for Stantec, has over 17 years of experience in the design and construction industry. Jeff Lynch, PE, Senior Partner, Mechanical Engineering, has over 20 years of experience in the architectural, engineering and construction industries.
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