Fuel and oxidizer. Together they make propellant, which can be used to launch a rocket – but for the best results, you need to find the right ratio. Too much of one or the other, and your exhaust velocity begins to drop. Less exhaust velocity means less thrust — and less thrust means you will not go to space today.
This is what happens when you build an extremely powerful vortex cannon, loaded with "one of the most dangerous gas mixes in the world," to fire it against houses made of straw, sticks, and bricks, like the big bad wolf.
As part of a BBC science show called Bang Goes the Theory, inventor Jem Stansfield climbed up the side of the 140-foot BBC building using "vacuum gloves" made from an ordinary vacuum cleaner.