Halon 1301 was developed in a joint venture between the U.S. Army and DuPont in 1954, and introduced as an effective gaseous fire suppression fixed systems agent in the 1960s, and was used around valuable materials, such as aircraft, mainframe computers, and telecommunication switching centers, usually in total flooding systems. It was also widely used in the maritime industry to add a third level of protection should the main and emergency fire pumps become inoperable or ineffective. Halon 1301 was never widely used in portables outside military and spacecraft applications, due to its limited range, and invisible discharge. It does not produce the characteristic white cloud like CO2 and is difficult to direct when fighting large fires. Halon 1301 is ideal for armored vehicles and spacecraft, however, because it produces fewer toxic by-products than does Halon 1211, which is critical for combat or space conditions where a compartment may not be able to be ventilated immediately. Halon 1301 is widely used by the U.S. Military and NASA in a 2-3/4 lb portable extinguisher with a sealed, disposable cylinder for quick recharging. Other agents such as CO2 and FE-36 (HFC-236fa) wet chemical are largely replacing halon 1301, however, due to environmental concerns. Civilian models in 2-3/4, 3, and 4 lb sizes were also made.