What is the difference between pepper spray and tear gas?

Pepper spray is back in the news in California. Students at Santa Monica College were pepper sprayed by the police during their ultimately successful protest of higher fees for the most popular classes. Other high profile clashes with the police have included the tear gassing of Occupy Oakland protesters earlier in the year and the notorious misuse of pepper spray by a University of California police officer against students at UC Davis.

Every time one of these incidents hits the news, the scientist in me wonders what the difference is between pepper spray and tear gas. My own experiences with tear gas in protests in Oakland shed little light on the distinction.

Both pepper spray and tear gas are classified as non-lethal irritants, though incidences of death from pepper spray have occurred. Pepper spray actually does come from the active compound in peppers, capsicin. Tear gas can be a couple of different chemicals, including a variant of capsicin, but the gas most commonly used on protesters is “CS gas,” or 2-chlorobenzalmalnonitrile, or, more rarely, “CN gas,” or phenylcyl chloride.  The commercial product Mace can contain different combinations of both capsicin and either CN or CS gas.

Tear gas being used in protests in Athens, Greece

An important distinction between tear gas and pepper spray, besides the chemical distinction, is the delivery method. Pepper spray is usually aerosolized from a hand-held spray can. [Note: Best practices of pepper spray use are not well demonstrated by Officer Pike at UC Davis.] Tear gas, when used for crowd control is often shot from “grenades” which explode to release the compound which is suspended in a solvent.

Now to the big question: how do I protect myself from the harmful effects of tear gas and pepper spray? As with most things, abstinence is the only wholly effective preventative measure. But to those of us who are unlikely to stop protesting altogether, I’ve found a few additional helpful pointers:

1. The advice to avoid wearing lotions or contact lenses to protests is valid. They can trap the chemicals in tear gas to your skin or eyes.

2. I’ve heard that the effects of tear gas are best nullified by both acid, like vinegar, and base, like and antacid solution. That said, I’ve yet to find reputable evidence that breathing through a bandana soaked in vinegar, a common piece of advice to protestors, is helpful at all. A damp rag may work just as well. Similarly, the antacid solution recommended by many can do a lot to cool the burning sensation from pepper spray or tear gas, but soap and water will work better to actually remove chemicals.

3. Long term toxicity issues can be avoided to some extent by washing any clothes exposed to tear gas several times.

Happy protesting!