Most hazards you’ll find on a construction site are big and generally obvious. It might be the inherent danger of certain power tools, the possibility of an electric shock, or the potential for a fall. Because workers recognize these hazards, they can take steps to avoid or minimize them.

But they should be just as concerned about a hazard they might need a microscope to see. It’s a living thing — a simple organism that’s always around us. We usually don’t even notice it until there’s a big stain on the wall or is shows up on that chunk of cheese you planned to eat. It’s mold, or more correctly, molds, because there are many different types.

Molds are a category of fungi that play important roles in our lives. While some molds make that chunk of cheese unpalatable, others make cheese possible. You can thank others for those fall leaves that disappear by spring. But when the wrong types of mold spores show up in the wrong places, they create potentially serious problems for workers and those who occupy structures.

We generally think of molds as unpleasant. They make surfaces appear to be unclean, and they often give off obnoxious odors. Those sensory issues are minor when compared to the effects upon health. For example, molds can trigger asthma attacks. Some molds produce what are known as mycotoxins, which some scientists suspect are at the heart of many illnesses. These tiny organisms can even compromise the structural integrity of wood-framed buildings.

Right now, more than 100,000 species of mold are quietly doing their work throughout the world. This article cannot possibly provide a detailed examination of each, so we’ll instead focus on practical strategies for avoiding mold’s development and how workers should remediate mold encountered on the jobsite.

Molds can grow easily anywhere that they find sufficient moisture, oxygen, and food. You can’t see them without that microscope, but molds spread microscopic seeds call spores that constantly float around us, no matter where we are. If those spores land in a damp area with access to the right kind of food — a particular species may thrive on anything from wood, to paper, to household dust — they’ll begin to grow. The new molds will send off more spores that will continue the cycle.

It’s just about impossible to eliminate mold spores from the air, but you can make them unwelcome and unable to reproduce. Since molds thrive on moisture, minimizing water and humidity is usually the first and most effective step. Improving air circulation and exposure to light also reduces moisture.

A critical element of mold prevention is addressing moisture issues as quickly as possible. Any type of water leak, flooding, or condensation should be addressed and cleaned promptly, ideally within a day or two. In addition to cleaning wet areas, identify and repair the source of the moisture. Take steps to reduce the indoor relative humidity to 60 percent or less, and properly ventilate any devices that produce moisture.

Remediating mold involves more than simply cleaning it up. You must ensure workers and other users of the space are not needlessly exposed to airborne mold created during cleanup. Second, you must remove all visible mold and any damage that was created. Finally, you need to take steps to ensure that an underlying problem does not cause a recurrence.

That’s why you need a plan. Just handing a worker a mop and a scrub brush won’t lead to an effective resolution. In cases of widespread mold, you may need to bring in a specialized contractor with extensive experience in mold remediation.

You plan should detail the work that is to be performed, the equipment and chemicals the workers will use (including the appropriate Personal Protective Equipment), procedures for doing that work, how workers should dispose of contaminated materials, steps to be taken to prevent a recurrence, and how the area will be monitored.

As much as possible, work should be scheduled when areas are unoccupied. If that isn’t practical, the plan should explain how to limit exposure to mold spores, dust, and other potential contaminants. There is no single best solution. The choice of strategies depends upon the nature of the structure and the mold contamination, as well as available ventilation.

Workers should wear the correct type of PPE, which may include rubber gloves, eye protection, and a respirator. Other protective gear such as rubber boots or hazmat suits may be needed depending upon the nature and extent of the contamination. The plan should also spell out how workers will be decontaminated at the end of work, if needed. You also need to know if any workers have a mold allergy, conditions such as asthma, or an impaired immune system, so their health may be protected.

Often the first response is to apply a biocide such as chlorine bleach to the affected area. However, biocides alone are generally not the best solution. Even after most molds have been killed, they can still create allergic or other responses in people with sensitivities. Even a highly effective biocide may leave mold spores behind, and if the underlying conditions have not been protected, the mold will return. Biocides can also have negative health impacts, especially on people with suppressed immune systems and can even be toxic in larger amounts.

Because molds are a form of fungus, you may be tempted to use a fungicide. However, most fungicides are intended for outdoor applications, and using them indoors can create a toxic situation.

Before beginning the cleanup, securely cover any surfaces that could be contaminated by airborne mold and dust with plastic. Sealing ventilation ducts and grilles before work begins usually makes sense unless they will provide the primary source of ventilation for the work.

The specific methods for cleanup will vary based upon the nature and extent of the contamination. For example, wet vacuums can remove water from carpets and hard surfaces. Nonporous surfaces may be scrubbed with detergent and water or with a wet wipe. Once the remediation work has been completed and everything has dried, use a HEPA (high-efficiency particulate air) vacuum to remove any dust from the affected area, and then clean all surfaces with a damp cloth or detergent solution.

Any porous materials that show evidence of mold growth or water damage should be discarded. Materials that can’t be salvaged should be kept in closed containers or sealed bags. Larger items with significant contamination may need to be wrapped in plastic before disposal. Typically, they can be disposed with other construction waste.Once the area is completely dry, there is no visual evidence (or smell) of mold, and you’ve solved whatever caused the mold problem, the area is ready for occupancy.
Re-inspect the area periodically to ensure that mold and odors have not returned. Some people recommend airborne testing, but that can be expensive and complicated. In addition, there are few clear standards on airborne mold. If you’re thinking about a regular testing program, consult with an industrial safety professional or industrial hygienist about whether it’s the right choice for you.

One simple step that can help you stay ahead of mold is to get better at managing the humidity in the affected areas. An inexpensive humidity gauge will let you know if the indoor humidity is getting too high. You can also add a humidistat to your HVAC system to automatically make adjustments when humidity levels rise above a specified level.