I posted this here several weeks ago, but since the subject has come up again....
this is an article written for the National Law Enforcement Trainers Association online magazine... hopefully it will add some insight... it was written with the police patrol officer in mind, but certainly applies to anyone who carries aerosol defense sprays..
Hot or Not? The Myths About Pepper Spray
by M. David West, NLETA Charter Member
NLETA Online Magazine
February 9, 2003
Ever since 1974, when the first Oleoresin Capsicum (OC) product specifically developed for law enforcement began to get marketed and sold out of a garage in a south Florida home, Aerosol weapons have become increasingly popular. Unfortunately, outside of a short course taught at the basic academy, little exists for most agencies in the way of advanced OC training, and a multitude of myths about what OC is, how it works, and what it's capabilities and limitations are have risen over the last 3 decades. Like all defense tools, the proper use of OC requires training. This article represents no replacement for that formal training, but is written only in hopes of dispelling some of the most common myths and misconceptions regarding OC and its proper use.
Myth #1 - Percent equals pain!
It is commonly believed that the higher the percentage of OC in an aerosol unit, the more effective it will be. This is simply untrue. In simplest terms, the percentage of actual active ingredient in a unit relates much more to the amount of time it will take an exposed subject to decontaminate than it does to the amount of "heat" felt. The question to ask is 10%, 15%, or 20% of WHAT? Is the base pepper a jalapeno, cayenne, or a habanero? How refined was the pepper before it was used in the formula? These things obviously should make a difference.
The true measure of heat is determined by the SHU, or the Scoville Heat Units found in the canister. SHU is a culinary scale that was developed to measure the heat in peppers, and helps us to determine the effectiveness of various OC sprays. A green bell pepper is the base of the scale and holds a rating of 0 SHU. As a matter of reference, a jalapeno pepper typically rates between 3,000 and 5,000 SHU. Fox Labs 5.3 on the other hand is rated at 5,300,000 SHU. High SHU ratings are obtained through the hybriding of certain pod peppers and then through a detailed refining process. Placing a large amount of poorly refined, garden-variety peppers in an aerosol unit does not make it hot. When considering the purchase of a canister of OC always check the advertised SHU. If the manufacturer boldly advertises percentages, but refuses to place the SHU rating on the can, chances are there is a reason for this.
Myth #2 - Pepper Spray doesn't work on persons of certain ethnic backgrounds.
This is probably the single largest myth in the history of pepper spray. As a result of having "hot" diets, including numerous peppers, it is commonly believed that people of Hispanic origin may not be as readily affected by OC. The reality is that no pepper, no matter how often it is ingested is as hot as most law enforcement grade OC. Pepper sprays effect subjects both physiologically and psychologically. While it is possible for a goal directed person, or someone under the influence of drugs or alcohol to overcome the actual pain associated with OC and continue to fight, it is impossible for them to overcome the physiological effects on their bodies. OC, when inhaled, inflames the mucus membranes of the nose and throat, resulting in coughing and gagging, thereby making breathing difficult. OC will cause eyes to twitch spasmodically and close, causing temporary blindness and loss of balance. The capillaries in the eyes will dilate when exposed to OC, and a burning sensation will be felt on any exposed skin. Goal directed subjects may overcome the pain, but are still placed at a disadvantage by being exposed to OC by its ability to take away their vision and their respiration pattern. OC will effect everyone differently based on their individual pain thresholds and raw determination, but has no way of knowing a persons birthplace, diet, or cultural background.
Myth #3 - More is Better!
This is yet another falsehood. Most OC manufacturers recommend spraying an offender with ½ - 1 second, short "bursts." If more OC is needed, it is recommended that more short bursts are used. If multiple bursts do not place the offender into a non-assaultive position, it is time to try something else. Spraying an offender with bursts longer than 1 second in length can actually be counterproductive. OC aerosol weapons generally contain three basic substances in the container. An active ingredient of refined pod pepper is used to incapacitate the offender. A solvent is utilized to emulsify the active ingredient and place it in a liquid state. Lastly, a propellant is added to the canister that allows the solvent/active ingredient mixture to be expelled from the canister onto an offender. In order for the pepper spray to be most effective, it is essential that the propellant and solvents used in the formulation of the pepper spray be able to fall out of or evaporate from the mixture rapidly, so that the offender is only exposed to pure active ingredient, leaving nothing to get in between the offenders skin and the "heat" of the product. By spraying a subject with a long, continuous burst, one can actually experience a washing effect where the solvent and propellant, still in the mixture, wash the active ingredient from the intended target area (eyes, nose, and mouth) and onto a less reactive area of the face.
Myth #4 - All OC is created Equal.
Because OC is generally an unregulated product, there are a multitude of "bathtub blends" available at every discount retailer and convenience store in America, and it is generally believed that all pepper sprays are about the same in terms of quality and reliability. As stated before, it is important for the defense-oriented consumer to become knowledgeable about OC, and check the SHU and percentages of active ingredients in particular prior to any purchase. This however is not enough. As a rule of thumb I tell students and student instructors to never purchase an OC product anywhere they can purchase beer or blue jeans. Rely on established law enforcement supply shops and reputable gun shops to help you with your purchase. Only purchase products made by established, well known manufacturers, and check out the OSHA materials safety data sheet for specific ingredients whenever possible. If you wouldn't trust your personal safety or the safety of your loved ones with a bargain basement, used, unchecked firearm, why would you trust an unproven, bargain basement OC? The cost difference in discount brand pepper sprays and law enforcement grade aerosol weapons is incidental, and well worth the peace of mind that the extra dollar may cost you.
Conclusion
Pepper Spray is an effective tool that should be carried by all law enforcement officers. Firearms are not the answer to every defense situation, and it is essential that we have the proper tools available to us as the situation dictates; else we sacrifice officer and suspect safety. However, with any defense tool comes the responsibility to train and become proficient with it. If you currently carry pepper spray or intend to in the future, seek training and find out everything you need to know about it to reduce your personal liability and to maximize its effectiveness.
Stay Safe and Win at All Costs!
hope this helps!
(aggressive, annonymous balls of fur) 
In a split second it screeches to a halt and runs away wimpring. Thus, i was spared from being bitten, spared from the rabies shot that I might have to receive and spared from my housemate's lousy cooking cos my takeaway dinner was still safe. 