I don't carry often but keep handy a OC spray from Guard Aklaska , a 9 0z. size with a thumb removable safety key. This spray has one of the highest percentages of OC, 20% compared to the smaller 'purse or pocket sized' cans and even more potent than most all LEO carries. This one is supposed to deter even grizzlies ! It has an ingredient which opens skin pores and removes protective mucous from the eyes and nose to really 'sink in ' ! Here is a clip from the manufacturers descrip. :
In any aerosol product, there are three components; The active ingredient, the carrier or base, and the propellant. In pepper spray the active ingredient is capsaicin, not oleoresin capsicum(OC). The total capsaicin in a pepper spray can be thought of in the same manner as the octane rating in gasoline. It is in reality the qualitative strength rating of pepper spray. In the past, Schoville Heat Units (SHU's) was a rating used as a marketing ploy to sell pepper sprays. SHU's are determined by a taste test and are not recognized by the E.P.A. or any laboratory in the industry because of their obvious inaccuracy.
A pepper spray that reads 10%, 15% or 20% tells the consumer that, by volume, the formula contains that respective percent of OC. The percent of OC does not tell the consumer the qualitative strength of the active ingredient -- capsaicin. The A.O.A.C. method for testing oleoresin capsicum is the only method recognized worldwide. The three capsinoids that make up the percent of total capsaicin are the following: Capsaicin(%C); Dihydro-capsaicin(%DHC); and Nordihydrocapsaicin(%NDC).
The carrier/base is also a significantly important, integrated part of the pepper spray. Historically, distilled water, vegetable oil or mineral oil has been used as a carrier for pepper sprays. It is well known that water is the antidote to capsaicin. Those pepper sprays using distilled water as their carrier are usually priced very low and found to be ineffective. Animals, as like humans, possess oils and fatty tissues on their skin to protect them from burns and damage caused by the suns harmful UV rays. Vegetable and mineral oil do nothing more than add additional protection to the skin and mucous membranes, thus reducing the overall effectiveness or the active ingredient, capsaicin. It is also known that capsaicin can be destroyed by the suns UV rays within a period of 48 hours, leaving nothing more than the carrier, be it vegetable oil or mineral oil, which alone attracts all bear species.
The last component of pepper spray is the propellant. The propellant's sole purpose is to dispense both the active ingredient and the carrier. The propellant should be an environmentally safe ingredient that does not contain flammable or ozone depleting substances.
In our research, we at McNeil River Enterprises, Inc., Manufacturer of Guard Alaska© Personal Protection Systems, have found that capsaicin alone will not deter an aggressive animal attack or human assailant. Guard Alaska products are unique from all other pepper sprays. Instead of the conventional carriers used, our products contain a carrier/base that removes the protective oils from the skin and mucous membranes, and actually opens the pores of the skin, allowing the active ingredient -- capsaicin to penetrate, thus increasing its overall effectiveness. Our carrier has a greater density than that of water, thus allowing it to displace water. This is a desirable trait for use when the animal or human assailant is wet from rain or other causes.