updated 4/16/2012 1:54:02 PM ET 2012-04-16T17:54:02

About 30 Santa Monica College co-eds were doused with pepper spray by police during a protest on the campus yesterday.

A plan to create high-priced courses, was the source of the conflict. After protesters tried to push their way into a trustees meeting, "two officers were apparently backed up against a wall, and began using force to keep the students out of the room," according to the Associated Press.

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The country has seen its share of pepper spray incidents in the past year, including a notorious incident at the University of California Davis which was caught on video.

So, what is pepper spray?

Also known as oleoresin capsicum or OC, pepper spray is made from the same naturally-occurring chemical that makes chili peppers hot, but at concentrations much higher. Its effects include temporary blindness, coughing and skin irritation.

To make the spray used by law enforcement officers and police to control crowds, manufacturers take a concentrated oil made from chili peppers and combine it with water, glycol (a chemical used in shaving creams and liquid soaps) and a propellent such as nitrogen, according to Bob Nance, vice president of operations at Security Equipment Corp. The company makes pepper spray and other irritants at its Fenton, Mo., headquarters under the Sabre brand name.

"We get it in a red, oily viscous syrup," Nance said. "It's the same thing you will find in hot sauce, but in higher concentrations. It causes your eyes to shut and makes breathing difficult," Nance said. "It can cause coughing and choking, and a severe burning sensation on your face. But it's temporary, usually it lasts from 30 to 45 minutes."

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Pepper spray comes in several strengths, ranging from 1 percent to 10 percent OC. That's equivalent to 2 million to 15 million Scoville Heat Units (SHU), which is a measure of the potency of the chili pepper extract.

The sprays also come in two forms -- as a fogger and as a stream.

Pepper spray has been used since the early 1970s, when it was developed for FBI agents and letter carriers facing mean dogs.

As for its hazardous effects, a 1999 study, "Health Hazards of Pepper Spray," by Dr. Gregory Smith of the University North Carolina, found that in the 1990s, 70 deaths of suspects in custody of police were associated with the use of pepper spray. The deaths were blamed on asphyxia or choking by the victims who had been hog-tied by police, who were intoxicated or under the influence of drugs or had pre-existing medical conditions and whose death could not be blamed on the spray itself.

A 2001 study by the National Institute of Justice and conducted by the researchers at the University of California, San Diego used pepper spray on 34 subjects.

The results showed that those in the sitting position did not face increased risk of respiratory compromise or choking, but it did cause increased blood pressure, according to the study. The study used healthy young subjects, who were not subject to numerous sprays.

Although the use of pepper spray is widespread in the United States by law enforcement, U.S. troops fighting overseas are banned from using it in combat by international treaty. Vance said, however, that his firm does sell some to military police guarding prisoners.

This is an update of an article by Eric Niiler that originally appeared on DiscoveryNews on Monday, November 21, 2011.

© 2012 Discovery Channel

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