The combustion engine is the heart of a natural gas car. This uses natural gas or CNG (Compressed Natural Gas) instead of the usual mixture of petrol and air. A natural gas engine works like a conventional naturally aspirated engine, only the fuel changes. This means that its cylinders operate according to the four-stroke principle. First, the gas-air mixture is sucked into the combustion chamber through an inlet valve. At the same time, the piston moves downwards. In the second stroke, it moves up again when the valves are closed and thus compresses the mixture, which heats up simultaneously. The third step is to ignite the gas-air mixture with the spark plug. The resulting reaction pushes the piston down. The kinetic energy generated is transferred to the crankshaft via the connecting rod joined to the piston and distributed to the drive wheels via the gearbox. In the fourth stroke, the piston moves up again and pushes the combusted exhaust gases out of the cylinder. 
CNG (Compressed Natural Gas) is compressed natural gas, while LPG (Liquefied Petroleum Gas) is liquefied natural gas. CNG is stored as a gas under high pressure and requires special pressure vessels, while LPG is liquefied at moderate pressure and stored in suitable tanks. As a rule, CNG is primarily offered ex works for new cars, while LPG is often preferred by workshops for conversion to gas drive.
Yes, it is possible to convert a combustion engine to natural gas. LPG (liquid petroleum gas) is preferred by workshops for conversions. The conversion includes the installation of a liquefied gas system with a gas tank, an evaporator or injector as well as special lines. A LPG conversion may make sense depending on the mileage. However, it is important to consider the development of fuel prices.
In principle, the natural gas used in gas heating can also be used to run a natural gas car. However, since the compressed gas (CNG) is stored in the car’s gas tank at around 200 bar, further measures are necessary to generate the required pressure, which is not available at the standard heating gas connection in the house. A home filling station and the integrated compressor are required to compress the gas and build up the pressure necessary to refuel the natural gas car. The installation and connection of a home filling station to the gas supply is the responsibility of qualified gas installers.
Gas-powered vehicles can be used safely in everyday life and do not pose an increased safety risk. Both natural gas and LPG are non-toxic. The gas tank of vehicles containing compressed natural gas (CNG) is stored at 200 bar pressure, although the compressed-gas tanks are designed and certified for 600 bar. A safety valve allows controlled discharge of natural gas when required. The tanks of liquefied petroleum gas (LPG) cars are reliably dimensioned with 3.5 mm thick steel walls, designed for ten bar in everyday use and must withstand a test pressure of 40 bar without damage. A pipe rupture valve prevents gas from escaping in the event of leaking gas lines.