CHI or PRANA is a kind of energy which comes from several sources. The chinese medicin knows severals sorts of CHI(Sheng Chi and evil Sha-Chi). The are up to 43 Qi-Sorts discerned. The four most important are Yuan-Qi(original Qi), Zong-Qi(Breath-Qi), Ying-Qi(Food-Qi) und Wie-Qi(Defense-Qi). Other names for the Yuan-Qi are Inborn-Qi and Acquired-Qi for the Breath- and the Food-Qi.
The Yoga knows 5 Pranas - Prana, Apana, Udana, Samana, Yyana.
Mankind receives its CHI mainly through the food and through the breath. So the many sorts of breath-practices for beginners become understandable.

In chinese breath-therapy (see : Prof. St. Palos : Breath and meditation - chinese breath-therapy und scientific measurements) the rythm of breath is used together with healing mantrams (special words with a special effect and meaning).

On our planet Chi comes mainly from the sun. Several chemical substances can store this energy or store parts of this energy. Especially the plants are in contact with the rays of the sun and store this energy just as the air does.

Chi circles in man in the so called etheric body (not to be confused with the astral or spiritual soul) which is known as the system of acupunture. Even animals have such a body.
A.A.Bailey : A Treatise on White Magic - Rule Two - The Hindrances to Occult Study , gives further details ( see : Online ! )

In Raja-Yoga step 4 (7 and 8 of the UNIVERSAL PATH) is Pranayama, dh. control of the Prana or Chi. Franz Bardon, master of white magic, spoke of accumulation and concentration of the Prana.

In the more progressed disciple CHI circles in a broad stream (small cycle, big cycle). The chinese Qi-Gong-Praktices concentrate on this cycle (Mantak Chia : Tao-Yoga of the healing Chi). On step 10 the disciple has established the small cycle. But this Chi is not yet spiritual. Depending upon the specific path Chi can then be so much concentrated that the disciple can heal und gain some occult abilities.
But healing has two sides : It brings into contact with negative forces and with the negative karma of the patients !

The result of dark Chi can be illness ! Through certain forms Chi can be transformed into constructive or into destructive forms. This is one point of true Feng Shi.

Common man unconsciously transforms this Chi or "Sun-Prana" into dark Chi, and therefore he is a "sinner" (until step 10) .
In rooms which are rarely ventilated, in halls of industrial production, in the center of big towns ( especially when filled with lots of people or with car-traffic ) , in discotheques, in many pubs filled with men following low desires, in pubs for dancing, forms of dark Chi can be found, and of course they are generated there.
Rotating machines generate dark Chi, and dark Chi is gerated when burning old plants and oil.

The seeker should therefore strive for a pure life and avoid such things , and he must learn how to protect against and clean from such negative influences and how to transform the Chi.
But Chi is not equivalent with spirituality. True spirituality first begins on the 7 initiations, ie. on step 14. The highest aspect of, the primary CHI on the buddhic plane is Pranava or OM.

Another name for this world is "Mirror-World", because the astrale and material events are reflect here. This plane contains the "Akasha-Chronics" and a part of the memory and it stands in connnection to the material karma.

A Wiki about Prana
A Wiki about Akasha