Re-opening Buildings After Prolonged Shutdown or Reduced Operation

What hazards should you check for?

A temporary shutdown or reduced operation of a building and reductions in normal water use can create hazards for returning occupants. Hazards include Legionella (the cause of Legionnaires’ disease), mold, and lead and copper contamination from corroded plumbing. Other air quality pollutants like sewer gasses, volatile organic compounds, and more may be present due to reduced operation of the building’s HVAC system.

Legionella can develop in water systems, especially after not being used or shut down for a “prolonged period”. A “prolonged period” may be weeks or months depending on plumbing-specific factors, disinfectant residuals, water heater temperature set points, water usage patterns, and preexisting Legionella colonization. 1

Mold can develop indoors even without there being a water leak. Under the right conditions molds can begin to grow in days, weeks, or months depending upon building-specific factors, season, and weather variables. 2

For lead and copper can accumulate in stagnant water over a “prolonged period”, which may be hours, days, weeks, or months depending on plumbing and water-specific factors, the amount of time the water remains stagnant inside the pipes, whether there are protective scales or coatings present inside pipes that prevent metals from leaching into water, and the materials used to build the plumbing system. 3

Legionella and Legionnaires’ Disease

Stagnant or standing water in a plumbing system can increase the risk for growth and spread of Legionella and other biofilm-associated bacteria. When water is stagnant, hot water temperatures can decrease to the Legionella growth range (77°–113°F, 25°–42°C). Stagnant water can also lead to low or undetectable levels of disinfectant, such as chlorine. Ensure that your water system is safe to use after a prolonged shutdown to minimize the risk of Legionnaires’ disease and other diseases associated with water.


Loudoun County Mold Testing