Pepper spray is also known as OC, short for its chemical name Oleoresin Capsicum. One of the best general-purpose self-defense tools ever developed, most police in the US carry it.  Decades of street-use by law enforcement have proven it safe and effective.

What does pepper spray do to someone?  It inflames the skin and mucus membranes of the eyes, nose, mouth and throat.  It causes intense pain.  It makes the person sprayed in the face close their eyes, cry cough as if chocking, and be unable to speak.  It makes them feel that they can’t breathe, though they really can.  The effects can last from about 15 minutes for breathlessness to over an hour for the skin sensation of burning.

There are dozens of different sprays on the market.  To find the right one for you, consider: OC concentration, Scoville rating, canister size, and spray delivery system.  Oh, yeah, and price.

Police pepper spray is usually in the 5-10% range. Higher percentage of OC might actually not be quite as good as the lower ones, because it is harder for the larger quantity of pepper to atomize in the spray.  Also, above about 10%, having more OC in the can doesn’t make it work faster, and doesn’t hurt the attacker more; it just makes the effects last longer than an hour.  Since you won’t need nearly that much time to get away and call for help, a product in the 5-10% range is most appropriate, and less expensive.

Next consider the hotness rating, which is measured in SHUs (Scoville Heat Units).  Many brands don’t make this measurement obvious, but you can find out by calling the company. The most desirable range is around 2 million or more.  Again, a lot higher is not better; sprays in the range of 15 million SHUs have been known to cause eye damage when sprayed at close range.

Another important consideration is the can size.  If you have a small one, designed to fit on a keychain (bottom diameter about dime size), it might not have enough oomph to adequately take care of your problem, especially if you are attacked by 2 or 3 people.  A 2 oz can (bottom about quarter size) is better.  It still fits easily in your hand and in most pockets, but it isn’t so likely to fizzle out when you need it most.

Yet another OC choice is the nozzle spray pattern.  Most produce a fairly wide cone-shaped spray, like hair spray.  Some are foggers, which make even wider dispersion of the material – that might be less appropriate for use in a building.  Other options are a stream (which must be aimed more carefully than a spray, but doesn’t contaminate the surrounding area as much) and foam (which sticks to the person it is sprayed on, and also minimizes contamination of the surroundings).

Be wary of products that mix OC with some other defensive chemical; those may cause eye damage.

Buy pepper spray at police supply stores, gun shops, and stores that specialize in safety products.  There are also a great many Internet sources. Cost is around $20, low enough to consider getting two or more, one to have in your coat pocket or purse, another to keep at home.

Some of the major brands are American Defense, BodyGuard, Cap Stun, Fox, Guardian, Punch, Sabre Defense, Def-Tec, Pepper Gard.

Local laws vary, so ask a reliable source what laws you must obey.  For example, Massachusetts used to require a license, but as of January 2015, a license is no longer needed. Some states impose limits on the OC concentration, or age minimums on purchase.