While an air car produces no pollution running on already compressed air in its tank, pollution is nonetheless produced when the air is compressed, both while the car is moving and while it's being refueled. As we mentioned earlier, the vehicle's air compressor will probably run on gasoline, and this gas will produce pollution when burned.
The air compressor at the gas station will probably be powered by electricity. The production of that electricity may or may not pollute, depending on how that electricity is generated. For example, coal-powered electricity could produce substantial amounts of pollution. Cleaner sources of electricity, such as nuclear power or hydropower, will result in far less pollution. According to the Web site Gas 2.0, an air car in the United States would create about .176 pounds of carbon dioxide emissions per mile based on the average mix of electric power sources during refueling. By comparison, a Toyota Prius Hybrid, which combines a battery-powered electric motor with an internal combustion engine, generates about 0.34 pounds of carbon dioxide per mile. So, while the air car is not quite pollution free, it still represents an improvement over one of the most popular hybrid cars on the market [source: Nuccitelli].
Distance could also become a disadvantage, depending on your travel habits. The distance that an air car can cover without refueling is crucial because very few filling stations will have compressed air pumps available at first. If you only plan to use your air car for short commutes -- distances less than 100 miles --will be fine. However, the one-to-two hour wait for the car's built-in air compressor to compress a tank full of air could become a problem on cross-country trips. Zero Pollution Motors -- the American arm of MDI and the company likeliest to produce the first air car for the U.S. market -- aims to have a car available soon able to travel between 800 and 1,000 miles on one tank of air plus 8 gallons of gas [source: Cornell]. Early prototypes, however, have traveled distances closer to 120 miles -- good enough for your daily commute, but not quite adequate for longer trips [source: Motavalli].
What will happen if an air car suffers damage in an accident? After all, compressed air tanks can be dangerous. To reduce this danger, the air tanks are made of carbon fiber and are designed to crack, rather than shatter, in a crash. This crack would allow the "fuel" to escape harmlessly into the surrounding air. Manufacturers feared that air escaping from one end of the tank could produce a rocket-like effect and propel the car on a jet of air. The valve on the cars' fuel tanks has been placed on the side to minimize this effect.
Despite these precautions, there is some concern that the air cars' lightweight construction might make it difficult for them to pass stringent American safety requirements and that this could hold up the arrival of air cars in the U.S. marketplace. Other factors have come to the forefront as well, and we'll learn about those next.