I use expired bear sprays that have lost over 10 grams of weight to do test sprays. It's a great way to become familiar with the spray in a controlled environment (nitrile gloves, safety glasses, spraying downwind, etc.). That said, I've shot 5+ year old sprays that only went about 10 feet instead of the advertised 30+ feet! But still, you get a feel for the duration of the spray and intensity of the cloud, plus you don't blow some of the pepper out of your fresh bear spray.So I have had spray in my eyes.
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The directions on the spray said do a quick test shot.