Soft washing relies on the use of a chemical (usually sodium hypochlorite, a.k.a. bleach), a surfactant, and a gentle spray of water to kill organic growth on surfaces.
This 4 inch stainless steel nozzle injects and proportions soaps, chemicals or liquids at high pressure or low pressure without going through your pump, hose, or gun. The X-JET nozzle projects chemicals or other liquids to vertical heights of 40 feet or more, depending on your pressure washer.
This is a roof cleaning method which combines safe low-pressure nozzle attached to a pressure washing gun or wand with water and biodegradable chemicals/cleaning detergents.
One of many risk assessments on the WCA website. Make sure you do a search for the best for your scenario & adapting the form to your needs & risks. Full Roof Working Risk Assesment