With its two-part oxygen activation process Activox siding plus cleaner removes the toughest algae, mould and mildew to restore and revitalize outdoor surfaces to their original appearance. It is ideal for siding, awnings, patio furniture, boats, and RVs but should not be used on composite decking. Activox's two-part system requires on site activation before generating the amount of oxygen required to achieve maximum cleaning effectiveness. It also degrades rapidly enough to be kind to the surrounding environment. Non-toxic and biodegradable, for best results it should be used within 1-2 hours of activation. This 4L container covers 9 - 28 m² (100 - 300 ft²).