Indoor and outdoor mold can grow on concrete surfaces like patios and basement floors and walls. When mold appears indoors, it can present a health hazard. Outdoors, mold can mar the appearance of the patio and make the patio surface slick. You should remove this mold quickly, but without negatively affecting the environment. If you use harsh chemicals outdoors, you can kill plants due to chemicals in the runoff. Indoors you could impart chemicals into the air. There are means to avoid both problems.
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Use a pressure sprayer and pure water to remove mold from concrete indoors and out. Set the power sprayer on the most effective nozzle setting to blow the mold off the patio. Be aware that a too-concentrated stream can leave a mark on your patio. Indoors, use a power sprayer and a wet vacuum at the same time. As you blow the mold off the concrete, suck up the wastewater with the vacuum. You can also sweep the water into a nearby sump pump well.
Safe Chemical Products for Mold Removal
Several products are on the market for killing mold and mildew without harsh chemicals. The Environmental Protection Agency has approved Safe Shield and Oxy-Mold. Safe Shield includes an organic component that provides a sealant against re-growth of mold.
Borax, bleach, vinegar and ammonia all have the capacity to kill mold on concrete surfaces. Since they are organic chemicals, they will not be as damaging to plants and people if accidental exposure occurs. However, this is only true if you adequately dilute these household products. Bleach and ammonia, if not diluted adequately with water, can cause respiratory irritations. Use a scrub brush to apply the product to the mold in small batches. Rinse the area with clean water. Indoors, vacuum the wastewater away. Outdoors, spray the waste away with clean water from a hose.
You can kill mold and remove it from concrete by using a steam cleaner. You can rent steam cleaners normally used for steaming wrinkles out of draperies. Load water in the steam cleaner and let the machine warm up. Then blast the mold with spurts of hot steam. Rinse the area with clean water. Be careful to wear protective clothing and shoes and avoid direct contact with the steam. Steam can produce serious burns on bare skin.
Scrubbing and Scouring
You can also kill mold with elbow grease. Use a stiff pig-bristle or metal scrub brush to remove the mold by hand. You can also use an abrasive-like sand or household scouring powder to help remove mold with a scrub brush. Rinse the area thoroughly with clean water, from either a hose or a spray bottle and sponge.
The wastewater produced after rinsing the surface will contain mold spores. Wear protective rubber gloves and a mouth and nose mask to prevent inhaling these spores. Keep the area wet to prevent the spores from becoming airborne inside the house. If you are de-molding a large area indoors, seal off any ventilation ducts and doorways to other rooms. Wash your work clothes immediately after finishing the job to kill any spores on your clothing.