Humidity is Key

The key to controlling mold lies in a parallel ability to control humidity. “If the indoor humidity is above 70 percent, mold will tend to grow everywhere,” said Phillip Fry, a certified environmental hygienist, mold inspector, mold remediator, and author of five mold advice e-books. “The problem with air conditioning systems, when they are running, is humidity is below 70 percent, but often, especially in offices and commercial businesses, the air conditioning is turned off at night or during the weekends, and the humidity goes above 70 percent, causing mold problems inside the system, ducts, and the building. You have to monitor humidity readings in the building. Keeping the humidity low 24 hours a day is crucial.”

Mike White, CEO, Clean Air Systems of La. Inc., Shreveport, La., said in his home state of Louisiana he tends to see a lot of oversized air conditioners that don’t control humidity. “They control temperature, but they don’t control humidity. So, while temperature should remain around 74°, they turn the thermostat down because — due to the humidity in the air — they’re hot,” he said. “When that happens, the grille starts sweating. … When you keep the humidity low, you can have the same comfort effect with the temperature as high as 77°.”

And, according to Alan Wozniak, president, Pure Air Control Services, Clearwater, Fla., dehumidification must be maximized inside a building. “Obviously, any water intrusion events need to be handled expeditiously within hours of the event,” he said.

Mr. Clean

Clean ducts restrict mold growth. “Using HEPA vacuums within a facility is important,” Wozniak said. “Many will use high-efficiency vacuum cleaners, but those basically throw the dust from one place to another.”

Fry said keeping the indoor space clean should be the No. 1 priority. “Quarterly cleaning helps remove accumulated dust and dirt, ultimately preventing the growth of mold,” he said.

White said mold feast on dust or dirt within the ductwork. Eliminating such grime, he said, minimizes the potential for mold.

The issue then becomes what is the best-practice method for duct cleaning, and how often should a contractor address the ductwork? “That’s the $64,000 question,” White said. “If a consumer has a good filter system, keeps the system up to date, and has it serviced on a regular basis, you shouldn’t encounter a lot of dirt or dust. At the same time, it’s important to make sure the ducts are sealed. You want to definitely keep the ductwork clean, and make sure a reputable company is performing the work.”

Test Time

Regularly scheduled monitoring and testing help identify system deficiencies, prompting a professional to address issues in the early stages of growth.

Fry suggested contractors use some sort of air testing media to test the actual air that is coming from vents. “When the HVAC is running on fan ventilation, sample the air from several different registers for each system at more than one location,” Fry said. “Collect a sample from the airflow, then an air sample from outside as a control reference point. Have that lab analyze the sample for quantity and type of mold spores.”

Wozniak said having a professional come out on a periodical basis, likely twice a year, to do a baseline evaluation is a good step to preventing and solving indoor mold.

“(You want to) see how you’re doing in regards to ubiquitous allergens, not necessarily just mold, that’s one of them, but allergens in general,” Wozniak said. “Unless you have a class 10 clean room, you’re not looking for zero numbers, you’re just looking for normal. A lot of facilities do that to ensure they’re maintaining good IAQ.”

Additionally, White said if an unexpected event does occur, such as inclement weather or a broken pipe that allows water into a home or building, drying it out should be an immediate move to avoid mold.

“Get somebody out there to put dehumidifiers in and keep that water in check,” White said. “Don’t wait. Once it gets in there, it’s an ideal food source for mold.

“There’s a particular building here in town, they have a problem with the condensate drain pan overflowing, and this is in a commercial building. When the building was built, they weren’t thinking about overflow and the drain line is flat across the top. So, when it backs up, it floods in the walls. They ended up having a mold issue because they didn’t take care of it right away.”

Remediation Station

Sometimes, though, all good plans go bad. Despite best intentions, mold does occur.

One of the first big steps you can take is finding the source of the mold after doing an investigation of exactly what happened and what went wrong. “Of the investigative findings, what is it? How much is there? Can it be cleaned or removed,” Wozniak said.

White said whatever caused the mold to build up should be found first. “You don’t want to be remediating when you have water running down walls,” White said. “Of course, if you have a busted pipe, and we run into that from time to time, you have to get access to that. But make sure you have a containment built, engineering controls, and air scrubbers in there to control anything that might be airborne. If you have damaged sheet rock, get it out of there before it has an opportunity to grow mold. You want to get that stuff out and get rid of it.”

Wozniak agreed, saying if the mold is within an HVAC system, finding the underlying problem and figuring out why it’s doing what its doing is a crucial step.

“We have UV lights and stuff, and those are things that are good, but they are very limited in what they can do,” Wozniak said. “We’re too fast to just throw UV lights into a system, but then downstream you have these millions of colonies of mold spores that the UV light is never going to touch. UV lights are nice and good as a proactive measure, but you really have to address the problem at its core.”

The next step should be getting the area tested.

“If it’s obvious there is a mold problem, don’t go over there and start beating it with a hammer,” White said. “You don’t want to get it airborne. If you find mold in a building or a home, call somebody who knows what they are doing and is a licensed mold remediator.”

Gas ‘Em

Fry suggested two tactics to remediate the mold.

The first step is to inject a high-output Ozone treatment for about eight hours.

“Inject that for maybe eight hours into the return air duct, so it goes through the equipment after you take the filters out,” Fry said. “It will go through all the ducts and then come out into the rooms to kill mold spores and mold growth. Ozone is very underutilized by HVAC contractors because they don’t have a working experience with it. It’s very powerful.”

He also added that fogging is a very effective method for remediating mold. “Use a fogging machine to fog an Environmental Protection Agency (EPA)-registered fungicide into the ductwork,” Fry said. “There are fungicides that are approved by the EPA for use inside air conditioning ducts. Check with a supplier and locate a mold killer that is good for ductwork, then fog it throughout. It kills the mold and deposits a preventive coating inside the ducts to help prevent future mold. Ozone goes everywhere, that’s good. Fogging also goes everywhere.”

The Final Steps

Perhaps the most important step an HVACR contractor can consider is to keep the ductwork clean. “If you have an air-handling system with an interior-lined unit, and that liner has gotten wet as a result of moisture carryover, or a primary drain clog, you can’t un-wet wetted insulation,” Wozniak said. “It doesn’t happen. You typically will have to remove and replace that insulation. Sometimes, what we will do is remove that liner and replace it with a closed-cell material. If you pour water on it, it’ll just bead up. You see that material in some of the newer, more efficient air-handler systems, but not as often as we’d like to see.”

Just like it was at the beginning, the key element to avoiding and remediating mold is making sure the area is dry, because it’s that moisture that helps breed mold.

“After remediation, you want to make sure the structure is dry,” White said. “After you get the sheetrock out, you want to measure the moisture content and make sure it’s dry. If it’s not dry, you’ll need to run dehumidifiers to dry the structure out. Typically, you’ll want to go in and clean it real good and put an antimicrobial over that once remediation is complete.”

Publication date: 8/12/2013 

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