Pepper Spray Basics

Despite how confusing the marketing for pepper sprays can make it seem, the basic workings of pepper spray is fairly simple. Pepper spray contains some of a family of chemicals called capsaicinoids, and those chemicals are responsible for the burning, coughing, sneezing, etc. At the end of the day, it is the percentage of the spray that is each of the capsaicinoids that determines the heat of the spray itself.

Why do I say each of the capsaicinoids? It is because there are five primary capsaicinoids, and they fall into two basic levels of heat. Two of them, capsaicin and dihydrocapsaicin, are basically the same strength, and are roughly 1.7-2.0 times as strong as the other three. So, if every spray told us what percentage of the spray's contents were each capsaicinoid, we'd have a perspicuous representation of the raw heat of the spray.

As life would have it, of course, no company indicates their spray's heat in this way. Instead, there are two primary ways companies indicate the strength of their product. The first, and far most common among self defense sprays, is to indicate the spray's OC% and the SHU, or Scoville Heat Units, of the OC. OC is short for oleoresin capsicum, and is the part of the spray that is actually derived from peppers; in other words, the OC is where the active ingredients are. The OC%, naturally, is the percentage of the spray that is OC. Scoville Heat Units are a subjective measure of spiciness attributed to, you guessed it, a chemist whose last name was Scoville. Basically, the SHU rating of an OC, or of a pepper, of a salsa is the degree to which it must be diluted before the spice can barely be tasted. Now, when pepper spray manufacturers refer to the SHU of their spray, they are actually referring to the SHU of the OC (unless otherwise indicated; some brands, like Heatwave, only test the heat after it has left the can).

Having said that, since OC% is the percentage of the spray that is OC, and since the reported SHU of a spray is the SHU of the OC, we can get a rough estimate of the raw heat of the spray by multiplying the OC% by the reported SHU of the OC. So, a 10% OC spray listed as 2,000,000 SHU can be (again, roughly) thought of as outputting a spray that is 200,000 SHU. This is important because some manufacturers emphasize the SHU of their spray, but don't point out that the OC comprises a tiny percentage of the spray, or do the opposite and point out that the spray has a large amount of OC in it, but ignore that the OC is quite weak.

As I have emphasized, though, this is only a rough estimate of raw heat. It is definitely not the alpha and omega of pepper spray effectiveness. For one thing, since pepper spray manufacturering is not regulated, there's no guarantee that the company's claims are even true. A company that claims a 10% OC, 2,000,000 SHU spray might actually turn out a product that is 7% OC, with an OC that is only 1,500,000 SHU. The difference in raw heat would be noticeable! (200,000 SHU spray out the nozzle in the first case versus 105,000 for the second). Second, pepper spray effectiveness is affected by other factors, like delivery method, a topic we will address soon.

I mentioned above that there are two main ways of marketing the strength of pepper sprays. The first, which we just examined, is most common for self-defense sprays. This second one is more common for bear sprays (pepper sprays designed to deter bears, reasonably enough). This second method is to list the percentage of the spray that is capsaicin and related capsaicinoids, or CRC%. For example, the EPA, which regulates bear sprays, requires that bear sprays have at least 1.0% CRC and no more than 2.0% CRC.

There is a problem with this, however. Remember what I said earlier about there being 5 capsaicinoids, with 2 of them being clustered near the theoretical maximum? Capsaicin is 16,000,000 SHU, and dihydrocapsaicin is usually put around 15,000,00; remember, those figures are subjective and not etched in stone. The other three, though, range from 8,000,000 to 9,000,000 SHU. So, a spray containing only 2.0% CRC, but with all of it coming from capsaicin, would be expected to have roughly 320,000 SHU coming out of the nozzle, while another with 3.0% CRC, but with all of it coming from the weakest capsaicinoid, would be expected to have roughly 240,000 SHU coming out of the nozzle.

The result of all this is that since none of the pepper spray manufacturers are required to indicate the strength of their sprays by listing the percentage of the spray that is each of the capsaicinoids, and are not regulated, the manufacturer's claims can only be taken to be a (very) rough indicator of the spray's hotness. This is what necessitates subjective testing of the spray's effects. Objective testing of the spray's contents would be very nice, but I haven't the money or equipment to engage in testing that extensive.

The final piece of this puzzle is the delivery system. OC is almost always used in a spray, and then there are three basic spray patterns used. The first is a narrow stream, which is easier to use when there's a stiff breeze blowing about, but requires more precision in aiming. The second is a fog pattern, which generally has a shorter range, is more affected by wind, but requires less aiming. It also affects the respiratory system more easily, since it can be breathed in more readily. That last factor is the reason I tend to prefer fogs or cones (cones are basically a more narrow fog, so you get the best of the stream and fog worlds). The final distinct patter is foam/gel. These are also easier to use in wind, but they are also easier to clean off, which is excellent for a controlled situation like a prison (where they are most common), but not so great in a self defense situation. As a side note, one of the reasons the OC% * SHU formula can't be the final word on pepper spray effectiveness relies on the behavior of the fog patterns. For a fog to work well, it has to be turned into very fine particles; however, OC is an oil, and oils don't very much like to be turned into fine particles. So, even though a 2% OC at 5,000,000 SHU would be expected to output 100,000 SHU, and 20% OC at 500,000 SHU would be expected to do the same, the former would likely be more effective as a fog, since the latter would be quite oily.

Well, that rounds up the pepper spray basics. In the next post I'll briefly outline the methodology of the tests I will be doing with pepper sprays, and then it'll be off to the races with testing!