By Doug Hoffman

During the imposed coronavirus pandemic shutdown, will the buildings you typically care for start to develop mold? Over the last and next few weeks or more, many buildings will be vacated because of “stay-at-home” orders, and they will sit unoccupied until the current crisis is over. Will we return to those buildings after the shutdown to find a huge mold problem?

Most of us were not prepared for this event and now find ourselves wondering what can be done to reduce the possibility that the building to which we return will be contaminated. A few simple steps could eliminate that potential problem.

Eliminate mold beforehand

Our buildings are designed for comfort and energy efficiency. The tightness of construction, the lack of fresh air, and our reliance on air conditioning have made our buildings prone to becoming petri dishes when the controls are shut down.  Buildings, both commercial and residential, were designed to be lived in. So, what can happen when they sit unoccupied for an extended period?

I was in the construction field in Florida where, every winter, we would get an onslaught of “snowbirds.” That wasn’t a derogatory term but a description of those who owned homes in the south but only came from the north in the winter to avoid the snow and enjoy the Florida beaches. Five to six months out of the year their Florida home sat unoccupied, and they often returned to mold-infested environments. Mold spores that were lurking in the settled dust, found an adequate food source of organic materials (dead skin cells, insect parts, etc.) and with the air conditioners off and humidity levels rising, mold was a happy camper. Could that problem have been avoided? The answer is “yes.”

A few tips to follow before you close the building include:

  • Do a thorough cleaning, including all horizontal surfaces. Areas where dust has settled, like door jambs, the top of bookcases, even chair-rails and baseboards, are often neglected in our routine cleaning. Care should be taken to make sure every surface has been wiped down.
  • Make sure the refrigerator is cleaned out and the trash removed and emptied. There is nothing worse than coming back into an environment where spoiled food has been rotting for weeks.
  • If possible, assign someone to go back on good weather days and open a few windows to allow the fresh air to come in. The natural sunlight and fresh air are great oxidizers of microbial contaminants like mold, bacteria, and viruses. It will help avoid that stale smell that might be there if you don’t do this. That includes leaving the blinds and curtains open to bring in the sun’s freshening rays.
  • Your air conditioning system is primarily a dehumidifier, so where possible, have it operating on the humidistat, if it has one, to maintain the relative humidity below 60%. If it doesn’t have a humidistat, use the thermostat and set the temperature at 80 degrees, which will cause it to run periodically throughout the closedown. This will help keep the indoor environment drier, and we all know mold does not grow when it is dry. 

Before reopening

When you return, or just before the building is reoccupied, you might consider an assessment by a professional NORMI Certified IAQ/Mold Assessor. They are trained in evaluating the presence of mold and other IAQ contaminants and can make recommendations for the reduction of such, should there be a problem.

Before you return, take a little time to go inside. Utilize your sense of smell to detect any changes in the environment. Trust your senses, as you might be the canary in the coal mine that detects the problem before it becomes a problem. Open the building to fresh air and turn the HVAC system back on. With a little attention to detail and an awareness of the potential problem, you can be sure that you and your employees are moving back into a safe and healthy environment.

Watch the follow-up video interview with Doug Hoffman. 

For more information, go to our website at, call 877-251-2296, or email [email protected]


Doug Hoffman is the CEO of NORMI, the National Organization of Remediators and Mold Inspectors. He can be reached via e-mail at [email protected].