OC spray, or pepper spray as it is more commonly called.
Oleoresin Capasin (OC) is concentrated heat from a hot-pepper plant. It is an oleoresin, which means it sticks to the skin and cannot be simply rubbed away, and it is an irritant, which means that the reaction does not rely upon allergies or sensitivities. Only about 1 person in about 10,000 doesn't really react to the stuff, so it can be an effective mid range defense tool.
If OC gets into or near your eyes, your eyes will slam shut and begin watering profusely; getting them open again is NOT going to happen just by willing it so, but you can reach up and pry one eye open with your hand if you keep your wits about you. Snot production kicks into high gear. The hands usually drop whatever they're holding, and reach for the face in a reflexive motion. The skin will burn like a bad sunburn or worse. If the OC gets down into the airways, breathing burns like fire and the person will have the sensation that they are choking or suffocating (they won't be, unless they are among the truly miniscule portion of the population who experiences an anaphylactic allergic reaction to the stuff).
All of this tends to stop the attack. That's the good news.
The bad news is that these reactions can take up to 5 seconds before they begin, and a lot of very bad and very permanent things can happen during that 5 seconds. Furthermore, if the attacker knows the victim is armed with pepper spray, there are certain specific things he can do to protect himself from the spray, or to mentally prep himself to fight through the reaction. Pepper spray does not make a good "stop or I'll use this" type of deterrent for that reason. (And any ex-con has very likely been sprayed before, knows what it'll do to him, and knows he can fight through it if he must; warning this type of person that you are about to use OC spray just preps him for a fight.)
You can get OC in three basic spray patterns: a fog, a stream, and a foam.
The foam was intended for use inside correctional facilities and other places where contaminating the air was a concern. I'm aware of at least two jails where they're no longer using the foam pattern because inmates have learned to simply swipe the foam off their skin and then smear it into the faces of the guards. The foam is least likely to get into the attacker's lungs, so scratch all the "I'm suffocating" stuff above; and unless you score a direct hit on the attacker's face you won't get the eyeball reactions either, leaving only the bad-sunburn sensation on whatever patch of skin you do happen to hit, and maybe not even that if you hit his clothes rather than his skin. So aim it carefully.
The stream was designed to combine the advantages of the fog with the advantages of the foam. It is more likely to get into the attacker's eyes, but still won't get into his lungs unless you are very fortunate and he was inhaling with his mouth open at the moment you hit his face. Like the foam, however, it is less likely to contaminate the user herself than the fog is. And like the foam, it has to be directly aimed at the attacker's face; a near-miss won't do anything useful.
The fog is most likely to get the full reaction: eyes, nose, lungs, skin. It requires the least precision in use, and a near miss with it is almost as good as a hit. It is quickest to disperse in the open air, however, and most likely to contaminate the user as well as the attacker.
The intensity of OC is measured in Scoville Heat Units (SHU), and also by the percentage of product within the can. In order to get the true, at-the-nozzle effectiveness rating, you multiply the SHU by the percentage of product. This multiplication gives you a common denominator allowing you to directly compare a can of OC with an SHU of 10,000 at 2% with one with an SHU of 8,000 at 5%.
Most instructors will tell you to use OC in 2-second bursts, and to immediately move to one side after you spray the attacker. The attacker will very likely lunge directly for the spot he last saw you in, with his arms wide open to try to grab you. You cannot just spray and stand there to see what happens. Flee to one side or the other rather than straight back for your best chance of getting away.
Fox Labs produces probably the best-regarded spray on the market. There are others. Stay away from any product that doesn't give you both the SHU and the %; stay away from any product that looks gimicky; and stay away from anyone charging $50 for less than a half-ounce of OC.
Some good old threads about using pepper spray and other non-firearms options:
http://www.thehighroad.org/showthread.php?t=254996
http://www.thehighroad.org/showthread.php?t=217761
http://www.thehighroad.org/showthread.php?t=179103
Also take a look through the subforum about non-firearms weapons.
pax
