Assuming you are looking to achieve Class 0 Level of Fire Protection and the fence has not been previously painted and meets the substrate requirements in the Technical Data Sheet we can recommend Zeroflame Fire Retardant Treatment.

This product is clear, lasts for the lifetime of the substrate once absorbed and can be over painted for decorative purposes - Waterborne stains or varnishes can be used over Zeroflame Fire Retardant Treatment as long as they are compatible, non-flammable and will dry. We always recommend to try a small sample area first to ensure the stain does not react with the Zeroflame Fire Retardant Treatment and will dry out.