Emergency / Disaster

Aftermath of the Flood: 6 Steps to Restoring HVAC Systems

Grainger Editorial Staff

After flood waters have receded, systems that weren't submerged in water are not necessarily ready to get up and running. Components of systems for heating, ventilating and air conditioning (HVAC) can still become contaminated, even if the system wasn’t submerged during the flood. Dirt and debris may have been deposited in the system and moisture collected on HVAC components may contaminate them with microorganisms like bacteria and fungi. That’s why all components of the system that were contaminated with flood water or moisture should be thoroughly inspected, cleaned of dirt and debris and professionally disinfected to prevent mold in the HVAC systemafter the flood.

We’ve assembled the below recommendations from expert government and academic sources for HVAC mold remediation. Follow them to make sure your HVAC systems are properly cleaned and remediated after a flood in order to provide a safe work environment.

The first thing to do with an HVAC system in the aftermath of a flood is to turn it off to prevent the spread of mold in the building. Then have the system cleaned as soon as possible.

How do you prevent mold in HVAC?

The Centers for Disease Control recommends taking the following steps to clean and disinfect contaminated HVAC systems to get them back up and running expeditiously:

1. Isolate the system: Use temporary walls, plastic sheeting or other vapor-retarding barriers to isolate the construction areas where HVAC systems will be cleaned and remediated. Use blowers equipped with high-efficiency particulate air (HEPA) filters to exhaust the area.

2. Take precautions to protect workers’ health: Workers must wear approved respirators to protect against airborne microorganisms. Increased levels of protection, such as powered air-purifying respirators, may also be necessary depending on the level of contamination. Follow the Occupational Safety and Health Administration (OSHA) standards for worker respiratory protection.

3. Clean and remediate the HVAC system: Flood-contaminated insulation surrounding and within HVAC system components should be removed and discarded according to applicable regulations. Contaminated HVAC filter media should also be removed and appropriately discarded. HVAC system components are then ready to be cleaned with a HEPA-filtered vacuum cleaner to remove dirt, debris and microorganisms. Experts at the University of Minnesota recommend that the vacuum system be capable of maintaining up to 1.0 inch of static pressure inside the isolated area of ductwork.

4. Rinse before disinfecting: Removing debris will require mechanically cleaning the surfaces of HVAC system components with a steam or a high-pressure washer before using disinfectant. Gasoline powered pressure washers should be used outside and away from air intake to prevent carbon monoxide hazards. Keep in mind CDC safety recommendations when using such tools. The University of Minnesota standards call for water pressure not to exceed 1,000 pounds per square inch gauge (psig).

5. Disinfect after cleaning: HVAC system component surfaces should be disinfected while the HVAC system is powered down with a solution of household chlorine bleach and water. Bleaches should not be mixed with cleaning products containing ammonia. The University of Minnesota standards call for the disinfection process to include sealing the supply duct lining with a fungicidal coating.

6. Resume HVAC operations: The HVAC system fan should be removed and cleaned, disinfected, dried and tested by a qualified professional before it is placed back into the air-handling unit. Before restarting the system, have its performance professionally evaluated. The HVAC system should be operated continuously at a comfortable temperature for 48 to 72 hours. If this process results in the spewing of objectionable flood-related odors, find contaminated areas that you didn't identify earlier and be sure to clean them. HVAC filters used during this flush-out process should be replaced prior to reoccupying the building.

Follow up: Once the HVAC system is operational, perform weekly checks to ensure that it is working properly. These checks should include inspecting the HVAC system filters and replacing them if necessary. Eventually, the frequency of the HVAC system checks can be reduced to monthly or quarterly inspections.

Cleaning and remediating an HVAC system after a flood also provides an opportunity to upgrade the system with higher-efficiency filters. According to the CDC, “This step has been shown to be one of the most cost-effective ways to improve the long-term quality of the indoor environment, since it reduces the amount of airborne dusts and microorganisms.”

Jeff Metherd has developed a wealth of emergency preparedness & response expertise in multiple roles at Grainger over the past 13 years. In 2005, he joined Grainger as a Government Account Manager, then assumed the role of Government Program Manager with a focus on Homeland Security for an 18-state region in 2008. In 2009, he developed the Grainger product offer for Public Health preparedness, and joined the Healthcare Corporate Sales team as a healthcare preparedness specialist in 2010. As Grainger’s emergency preparedness strategy manager, Jeff is actively engaged in efforts to drive continuous improvement in servicing our customers during natural disasters and other emergency situations.

The information contained in this article is intended for general information purposes only and is based on information available as of the initial date of publication. No representation is made that the information or references are complete or remain current. This article is not a substitute for review of current applicable government regulations, industry standards, or other standards specific to your business and/or activities and should not be construed as legal advice or opinion. Readers with specific questions should refer to the applicable standards or consult with an attorney.


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