This is a Demonstration of a Boeing 747 Modified by: Evergreen-International-Aviation-inc. According to the manufactures. Evergreen International Supertanker is (Modified) for fire-fighting applications at low altitudes.
Official website: "Evergreen's Supertanker utilizes a new type of pressurized system allowing the aircraft to fight fire from higher altitudes. (...) The system was designed to allow the Evergreen Supertanker to fly at a very safe altitude, 400 to 800 ft, and within its design envelope.
Also, the Evergreen Supertanker's tank system allows segmented drops. This means that the aircraft can drop its 24,000 gallons at multiple intervals while in flight. www.evergreenaviation.com...