Mold is a growth of tiny fungi that appears as powdery growth on various natural and household substrates.This growth generally occurs under moist conditions and can be very dangerous (and in some cases deadly) to humans. If your home has any type of mould, you need to take steps to clean it. Having mould on your patio does not make you safer simply because it is outside. Mold on the patio can easily find its way into your house and infect it with dangerous levels of toxins.
Close all windows and doors facing the patio. Place a tarp over them and duct tape it to the house. This will help to keep any mould spores from entering the house when you begin cleaning.
Don the safety goggles, face mask, and gloves. This will help protect your skin from the mould.
Fill up the five gallon bucket with a solution of four parts water to one part detergent. Saturate the brush with the soap solution.
Scrub the mould spot with brush and the soap solution until the mould has been cleaned away. Press hard to get the brush into the small cracks in the concrete.
Spray away the soap solution with a pressure washer. If you do not have a pressure washer, use a hose with the highest pressure you can generate. Spray the concrete until it is completely washed off.
Throw the gloves, goggles, and face mask in a trash bag while you are still outside. Double-bag the trash and throw it in an outdoor trash receptacle.
You should do this at a time when the patio will dry quickly. Moisture allows mould to grow and if the concrete remains wet, the mould may come back.
If you continually get mould in one spot, you may have a water leak under the patio somewhere. If this keeps occurring, you might have to pull up your patio so that you can fix the leak.