Natural gas is lighter than air, and so tends to dissipate into the atmosphere. When confined (for instance inside the trunk) it can reach it's explosive limit, which is from 5% to 15% in air. It is not odourless because an odorant is added to the otherwise colourless and odourless gas. Late model CNG vehicles (built after ECE-R 110) have a lot of safety devices that deal with these properties. An electromagnetic valve mounted at each gastank will close the tank in case of an accident or when the engine or the ignition is turned to the off position. A release limiter will also reduce the amount of gas that can be released in case of a leak in the gas lines. For service of the vehicles or in case the electromagnetic valve fails, the gastank can also be shutoff manually.
Oxygen sensors, or O2 sensors, are required to perform a critical function on your vehicle in the harshest of environments: Measuring the oxygen content of the exhaust just after it leaves the cylinders. The oxygen sensor has to accurately check this red-hot exhaust hundreds of times per minute and send that data to the vehicle computer. The fuel/air mixture hangs in the balance, and you're probably familiar with the symptoms of a bad oxygen sensor: Black smoke from the exhaust, a rotten-egg odor, and poor performance and fuel mileage. 
1. We need to be careful (as green-oriented folk) to distinguish between products that reduce emissions vs products that simply transfer emissions somewhere else. It is not true that a vehicle like this has no emissions. The emissions have occurred in the power plant that generated the electricity for the compressor.
If the power plant is fossil-fuel based then it only reduces emissions if the overall energy per mile is lowered. Unfortunately I suspect that the fact that the tax system skews petrol prices upwards vs centrally generated electricity will make the low running costs of this be assumed to translate to low emissions.
What is true is that if this technology is twinned with renewable (eg wind/solar) then it does have great potential. Again unfortunately there is the potential for nuclear proponents to suggest that this is a good way forward, based on it being away to convert nuclear energy into vehicle motion with no emissions. But how green do we view nuclear energy?
2. I have wanted a Mini cat ever since I saw one. But I want to own a Pink one. Is that possible and if you have one in stock please send me pictures. I believe that the Minicat is the new and improved car. It looks cool and saves the earth. But it dosent have a back seat. just kidding if you kno what I mean. Thanks! Katie
3.You hippies won't be happy until we all live in grass huts and ride bikes everywhere. Someone comes out with a new product that is revolutionary to say the least and you tear it down and discredit it as if it was a fraud. Whats really funny is, I don't know a single SierraClub member or "Environ-mentalist" who actually goes out and works in the forests or high country. They very people you bash (4x4 drives, dirtbike riders, etc) are the ones who fight to keep trails open and work hand in hand with BLM and the Forestry Department. If you ask me, the hippies are the real fraud.
4.Isothermal compression/expansion changes availability, thus acting as storage with a tank. The air car uses near isothermal. Like an electric car except less expensive, and no need for new batteries. Hope they get it out!!
BTW, look at www.annualizedgeosolar.com. Their technology for a self-heating/cooling house could be added to an existing house if someone was willing to do the work needed. I'm modifying my own - starting in May, 2005.
5.I have been watching the progress, or lack of it, on the air powered car for some time, but when will it be available? As for the arguement that emmissions are just transferred to the power station, that is stupid, at least at the power station there is the possibility of controlling emmission, this is not so with individual fossil burning cars.