The Scoville Scale is a measurement of the capsaicin concentration in a chile pepper. It is measured in Scoville Heat Units. The higher the number, the hotter the pepper.
BELL PEPPER - 2,500 SHU
In 1912, Wilbur Scoville devised a method to rate the heat in a chile pepper diluting an alcohol based extract until human tasters no longer taste the heat. The amount of dilution translates to the Scoville Scale. Today another method is used; high performance liquid chromatography (HPLC). Scientists can determine how many parts per million of heat-causing alkaloids are present in a chile pepper and multiply that number by 16 to get the chile pepper's Scoville Rating.