Wednesday, July 8, 2020

COVID-19 Reminder: Reopening Building Facilities With Caution

While some city facilities have reopened, others remain closed. Microbial hazards such as mold and Legionella, the cause of Legionnaires’ disease, can develop in facilities without proper care during the shutdown or without proper precautions prior to reopening.

Potential Hazards

Mold and Bacteria:

Mold and bacteria thrive in moist conditions. When buildings are unoccupied for long periods of time moisture problems may go undetected allowing mold and bacteria to spread. Leaks from roofs and plumbing can deposit moisture and remain undetected while buildings are unoccupied if not inspected on a regular basis. Additionally, traps in floor drains, toilets, and sinks can dry out allowing moist, bacteria-infested sewer gas to flow into a building and collect on ceilings, walls, floors, curtains, and furniture.

Mold and bacteria can also spread throughout a building if furnace filters became damp and contaminated during shutdown and the HVAC system is put back in use before replacing the filters. If HVAC systems with manually adjusted humidifying units have been operating during the shutdown with limited supervision, the humidifier may still be at winter settings introducing excessive moisture through the air distribution network.

People can be exposed to mold through skin contact, inhalation, or ingestion. Individuals who are immunosuppressed are at increased risk for infection from mold.


Legionella is a naturally occurring bacteria that can be found in lakes, rivers, ground water, and thus water distribution networks, and, if present, it bacteria is normally found at a very low level. Legionella grows best in large, complex water systems that are not adequately maintained at temperatures between 77-108 o F. During prolonged facility shutdowns hot water lines are idle for long periods of time and the water temperature can fall into the Legionella growth range. Additionally, building operators may lower the temperature level of water heaters trying to save on fuel costs, but in doing so may be creating an environment where Legionella or other bacteria can multiply. In cold water lines where building air conditioning systems are not operating during shutdowns the ambient temperature around stagnant water lines and cooling towers can also fall into the Legionella growth temperature range.

Inhalation is the most common route of exposure for Legionella. The breathing in of small water droplets containing Legionella allows the microbes to enter the respiratory system. This transfer of water into a breathable source can include cooling towers, sinks, toilets, showers, decorative fountains, and hot tubs.

Double Jeopardy

Coronavirus is a respiratory virus usually affecting the lungs and weakening the immune system. Combining the respiratory hazards and immune deficiency issues created from the COVID-19 pandemic with an additional respiratory infection hazard from mold, Legionella, or other forms of bacteria can only make a bad situation worse. The most at risk individuals are people with pre-existing conditions like asthma, have allergies to mold, or have a weakened immune system.


Fortunately, there is no need to reinvent the wheel as you plan to safely reopen your buildings. You can refer to the CDC Guidance for Reopening Buildings After Prolonged Shutdown or Reduced Operations. This CDC guide will cover minimizing mold and Legionella as buildings reopen risk in significant detail.

Looking for more information? Here are more resources you can explore:

Submitted by: Joe Gehrts, Senior Loss Control Coordinator

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