(so called "Clean Air") and Qi acquired from food and drinks (so-called "Grain Qi"). Looking at roles Qi is divided into "Defensive Qi" and "Nutritive Qi". Defensive Qi's role is to defend the body against invasions while Nutritive Qi's role is to provide sustenance for the body. To protect against said invasions, medicines have four types of qi; cold, hot, warm, and cool. Cold qi medicines are used to treat invasions hot in nature, while hot qi medicines are used to treat invasions cold in nature. looking at locations, Qi is also named after the Zang-Fu organ or the Meridian in which it resides: "Liver Qi", "Spleen Qi", etc. Lastly, prolonged exposure to the three evil qi (wind, cold, and wetness) can result in the penetration of evil qi through surface body parts, eventually reaching Zang-Fu organs. A qi field (chu-chong) refers to the cultivation of an energy field by a group, typically for healing or other benevolent purposes. A qi field is believed to be produced by visualization and affirmation. They are an important component of Wisdom Healing Qigong (Zhineng Qigong), founded by Grandmaster Ming Pang. Scientific view The existence of Qi has not been proven scientifically. A 1997 consensus statement on acupuncture by the United States National Institutes of Health noted that concepts such as qi "are difficult to reconcile with contemporary biomedical information". Practices involving qi Feng shui The traditional Chinese art of geomancy, the placement and arrangement of space called feng shui, is based on calculating the balance of qi, interactions between the five elements, yin and yang, and other factors. The retention or dissipation of qi is believed to affect the health, wealth, energy level, luck, and many other aspects of the occupants. Attributes of each item in a space affect the flow of qi by slowing it down, redirecting it or accelerating it. This is said to influence the energy level of the occupants. Positive qi flows in curved lines, whereas negative qi travels in straight lines. In order for qi to be nourishing and positive, it must continue to flow not too quickly or too slowly. In addition, qi should not be blocked abruptly, because it would become stagnant and turn destructive. One use for a luopan is to detect the flow of qi. The quality of qi may rise and fall over time. Feng shui with a compass might be considered a