HHO is a mixture of hydrogen (H2) and oxygen (O2) gases, typically in a 2:1 atomic ratio, the same proportion as water. This gaseous mixture is widely used for torches for the processing of refractory materials. HHO is what we add to our fuel mix in our engines and this is what gives us better gas mileage!
HHO will combust when brought to its autoignition temperature. For a stoichiometric mixture at normal atmospheric pressure, autoignition occurs at about 570 oC (1065 oF). The minimum energy required to ignite such a mixture with a spark is about 20 microjoules. At normal temperature and pressure, oxyhydrogen can burn when it is between about 4% and 94% hydrogen by volume. Abbreviation for Hydrogen Hydrogen Oxygen, which is what water (H2O) is broken down into.
HHO gas, also known as oxyhydrogen can greatly increase the fuel efficiency of cars in which it is used. HHO gas is created through a simple process of electrolysis - the car does not run just on HHO but rather a hybrid of gasoline and HHO which powers the car. HHO has been shown to increase fuel efficiency by as much as 60% in some cases.
More recently, HHO has been pressed into service helping cars to run on water. When talking about the automotive applications of HHO it is often called Brown gas. The electrolysis of the water stored in the car will then begin and HHO or Brown gas will be produced as a result. The air intake valve of the car's engine will pull this gas into the combustion chamber. When mixed with gasoline, this Brown gas gives vehicles dramatically better gas mileage.