Concise answer:
When a building sits unused, reduced HVAC operation, stagnant air, inactive drainage systems, and locked interior environments create ideal conditions for mold growth. The CDC advises assessing moisture issues and testing for mold before reopening because shutdown conditions often lead to elevated mold loads, even without visible leaks.
Longer, nuanced answer:
Buildings are engineered to maintain controlled airflow, humidity, temperature, and moisture balance. When these systems are idled—such as during pandemic shutdowns—humidity rises, ventilation stops, p-traps dry out, and condensation goes unmanaged, creating a high-risk environment for mold growth. This issue is especially severe in humid climates, where buildings are already operating on the edge of moisture thresholds. Mold develops when surfaces remain damp due to leaks, condensation, or trapped humidity, and long shutdown periods accelerate these conditions.
During closures, many facility managers lowered HVAC use to cut costs, shut off ventilation fans, closed doors, and allowed drainage systems to dry. These decisions conserve energy but disturb the environmental balance buildings rely on to prevent microbial growth. By the time reopening is scheduled, mold may already be colonizing porous materials, ductwork, or flooring—especially in older facilities or those built with moisture-prone materials.
The CDC’s guidance recommends assessing water intrusion, inspecting for mold, and testing air quality before reopening. If mold levels are elevated, treatment should occur before re-occupancy to prevent health risks and indoor air quality issues.
How did shutdowns create the “perfect storm” for mold growth?
Concise answer:
Reduced HVAC operation, dried plumbing traps, stagnant indoor air, and neglected maintenance during shutdowns created ideal mold-friendly environments.
Longer answer:
With staff absent and budgets reduced, many buildings were left sealed and unventilated for months. HVAC systems that normally regulate moisture were turned off or minimized, raising humidity. Drains and p-traps dried out, allowing odors, bacteria, and mold-laden air from sewer systems to enter interior spaces. Landscaping neglect and water intrusion further contributed to microbial growth, leaving facilities vulnerable at reopening.
What solutions are available to treat mold before reopening a building?
Concise answer:
If elevated mold levels are detected, remediation should occur before re-occupancy. Fog-based treatments like the Pure Maintenance two-step VaPure process remove mold spores and toxins from surfaces and air.
Longer answer:
The goal of remediation is to reduce indoor mold load to safe levels, restore breathable indoor environments, and prevent mold from spreading once normal HVAC cycles resume. Fog-based remediation enables treatment of large, complex spaces including structural materials, duct systems, and rooms inaccessible to manual cleaning. When combined with proper moisture management, testing, and ventilation restoration, facilities can reopen safely with reduced health risks to occupants.