Fire extinguisher useful in fighting fires with a particular group of fuel. Specifications for fire extinguishers are set out in the standard AS/NZS 1841, the most recent version being released in 2007. All fire extinguishers must be painted signal red. Except for water extinguishers, each extinguisher has a coloured band near the top, covering at least 10% of the extinguisher's body length, specifying its contents. In Australia, yellow (Halon) fire extinguishers are illegal to own or use on a fire, unless an essential use exemption has been granted, this is due to the ozone-depleting nature of halon. According to the standard BS
Cold gas thruster movement and activating the extinguisher. Because the gas is usually unheated, speed at the throat is low and very low performance is achieved; in a vacuum with nitrogen gas a specific impulse of 73 seconds can be achieved. The maximum theoretical specific impulse for nitrogen gas is 76 seconds. In the simplest approximation, the specific impulse is modeled as proportional to the square root of the (absolute) gas temperature, so performance rises as the gas temperature is increased. A thruster in which the performance is increased by heating the gas by an electrical resistance is known as a resistojet. Cold