Various Oleoresin Capsicum (OC) aerosols are often touted as having the highest SHU levels on the market. But what is SHU and how is it measured? SHU stands for Scoville Heat Units and is a standard used to measure the perceived heat of a substance. For example, a bell pepper has an SHU rating of 0, a jalapeño pepper has a rating of 2,500 to 8,000, and a habañero has a rating of 100,000 to 350,000 SHU. Typical law enforcement grade pepper sprays report an SHU level between 5-5.3 million.

How is SHU level determined?
SHUs are measured by diluting a solution of pepper extract in sugar syrup until the “heat” is no longer detectable to a panel of tasters, in accordance with policies put forth by the American Spice Trade Association. The degree of dilution determines its SHU measure. For example, a bell pepper, which contains no capsaican has an SHU rating of 0 because no heat was detected by the panel of tasters, even undiluted. Conversely, a habañero has a rating of 100,000 to 350,000 SHU, indicating the extract had to be diluted over 100,000 times before the “heat” was undetectable. The greatest weakness of the SHU level is that it is imprecise, since it relies on human subjectivity.

Capsaicin Content – A better measure
Rather than use a subjective scale, the only “percentage” one needs to remember is the percentage of major capsaicinoids also called % MC. The % MC can be physically determined in a laboratory, and is not a perceived unit of measure and is the only reasonable and repeatable way to quantify the level of heat-causing ingredients in an OC aerosol. But how hot does a formulation need to be in order to be effective and cause a momentary pause in combat?

How hot is hot enough?
Manufacturers of OC aerosols have gone to great lengths to determine the ideal % MC for use in law enforcement. If the capsaicin content is too low, the formulation may not have the desired effect on the subject, putting the officer at risk. A greater level of capsaicin content will be perceived as being hotter to the subject, causing more pain, resulting in a greater pause in combat or a more passive subject. However, the greater capsaicin content may result in increase decontamination times. It is widely understood that .02% capsaicin content is the most effective formulation to cause a pause in combat, while mitigating liability and risk. Recently however, some OC formulations have been developed that contain .04% capsaicin in an effort to create a faster reaction time and a longer pause in combat.

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