You may brave the jalapenos but pass on habaneros. You ask your friend how hot are they really? Her red-faced answer is "HOT!!!" Is trial and error the only way to find out? Fortunately not.
The food industry uses a rating scale developed by Wilbur Scoville which rates the heat of various chili peppers in Scoville units. This method uses a taste panel to taste dilutions of peppers until they can no longer detect any heat. A bell pepper is always 0, whereas a chipotle pepper may be 10,000 indicating its heat could not be detected at this dilution level. It's a subjective test so it isn't perfect. A newer method uses high performance liquid chromatography (HPLC) to detect and measure all chemicals known to produce the sensation of heat. For peppers, the chemical is capsaicin (pronounced cap-SAY-i-sin), also used in pepper spray and sore muscle ointments. These results are reported in pungency units which can be mathematically converted to Scoville units. The amount of capsaicin in a pepper plant depends on the climate, soil, and plant variety.
16,000,000 Pure Capsaicin
5,300,000 Police Grade Pepper Spray
2,000,000 - 3,000,000 Common Pepper Spray
800,000 - 1,000,000 Dorset Naga, Naga Jolokia
100,000 - 450,000 Habanero, Scotch Bonnet, Caribbean Red
50,000 - 100,000 Santake, Thai
30,000 - 50,000 Cayenne, Tabasco
15,000 - 30,000 Chile de Arbol
2,500 - 5,000 Jalapeno, Mirasol, Guajillo
1,500 - 2,500 Sandia, Cascabel
500 - 1,000 Anaheim, New Mexico
100 - 500 Cherry, Pepperoncini
0 Sweet Bell, Sweet Banana, Pimento
Photography by Sven Werk