1.   Another would be to sweep the fumes out of the empty space inside the tank, although venting the unburned fuel to the atmosphere would add to pollution.

2.   But each time a cylinder fires, the engine expels the exhaust gases using a mixture of fuel and air, and some unburned fuel escapes with the exhaust.

3.   Cold starts are the source of most hydrocarbons, which are unburned fuel, and carbon monoxide, which is partly burned fuel.

4.   In others, it has hopped and skipped around, leaving behind unburned fuel that can flare up unexpectedly if struck by an errant ember.

5.   They turn smog-causing nitrogen oxides, carbon monoxide and unburned fuel vapor into less harmful carbon dioxide and other gases.

6.   This ensures that the fuel burns more completely, improving efficiency and reducing the amount of unburned fuel that leaves the engine and must be controlled.

7.   Those engines use a small amount of unburned fuel as lubricant and then expel it into the water.

8.   Wynn led the fight for the ban, arguing that the engines discharge hundreds of thousands of gallons of unburned fuel into the lake each year.

9.   Another study conducted by Blake and Nobel chemistry laureate F. Sherwood Rowland suggested that unburned cooking fuel comprises half of the pollutants in the Mexico City valley.