<P> NO 2 is used as an intermediate in the manufacturing of nitric acid, as a nitrating agent in manufacturing of chemical explosives, as a polymerization inhibitor for acrylates, as a flour bleaching agent., and as a room temperature sterilization agent . It is also used as an oxidizer in rocket fuel, for example in red fuming nitric acid; it was used in the Titan rockets, to launch Project Gemini, in the maneuvering thrusters of the Space Shuttle, and in unmanned space probes sent to various planets . </P> <P> For the general public, the most prominent sources of NO 2 are internal combustion engines burning fossil fuels . Outdoors, NO 2 can be a result of traffic from motor vehicles . </P> <P> Indoors, exposure arises from cigarette smoke, and butane and kerosene heaters and stoves . </P> <P> Workers in industries where NO 2 is used are also exposed and are at risk for occupational lung diseases, and NIOSH has set exposure limits and safety standards . Astronauts in the Apollo--Soyuz Test Project were almost killed when NO 2 was accidentally vented into the cabin . Agricultural workers can be exposed to NO 2 arising from grain decomposing in silos; chronic exposure can lead to lung damage in a condition called "Silo - filler's disease". </P>

How can you determine whether nitrogen dioxide is a compound or a mixture