Fire  (Pao Chuan - Cannon Fist).
Fire is powerful and fast, often thought of as firing a cannon because of its explosive power..
The main organ for transmitting the energy is the heart.
 
Chi Gung (Breathing/Energy exercise) - Firing the Chi. 
Stand in Gung Bu (front stance) with your feet shoulder width apart (side to side) and twice shoulder width (front to back). Hold both fists near the jaw, about a fist distance away from the chin. The fists must be relaxed, and the elbows and shoulders sunk.
Bend the front knee to align with the front toes and hang your coccyx beneath the top of your head - see Fig1.
 
Using natural breathing (relax the Dan Tien and allow it to expand when you breathe in, and deflate as you breathe out), take a deep breath in and gradually sit back until the coccyx aligns with the heel of the rear foot, whilst turning about 30 degrees to the right - see Fig2.
Suddenly punch forward with the right fist, whilst breathing out, and at the same time raise the left fist up to the third eye, then drop it to the left temple - see Fig3 and Energy explanation of Fire.
Allow the body to recoil and settle back down into the hip joints.

Energy explanation of Fire:
Drive the energy stored in the rear leg and hips up through the spine, through the heart and  outward through the right fist (which suddenly punches forward and twists to a palm down fist), the left fist should twist to a palm out fist, at the same time - See Fig3.
Use the mind to imagine a flow of energy from the Dan Tien to the bottom of the rear foot (bubbling well) and into the floor,  and allow the right shoulder to go forward whilst still settled in its joint, at the same time energy flows from the Dan Tien to the right fist and out beyond into the air.
At the same moment imagine that energy flows from the left fist into the Dan Tien and from the left bubbling well into the Dan Tien. Immediately relax and settle back to a comfortable position - see Fig1.
 
For martial purposes reverse breathing should be used (relax the Dan Tien but don’t allow it to expand when you breathe in, this will create a slight feeling of tension in the body and the breath will go up into the heart area, drop the diaphragm and completely relax the Dan Tien when you breathe out), but the movement of the body should be smaller (train from large jings to small jings i.e. When you have warmed up with large gentle movements, you can practice for martial power in application with smaller movements of the whole body, whilst still trying to maintain the same feeling of power, using reverse breathing.