How long does it take for the effects of pepper spray to wear off? he good pepper sprays on the market will start to wear off after 10 to 15 minutes. They are the 2 to 5 percent capsicum sprays. Pepper spray with 15 percent capsicum may last up to 30 to 45 minutes. The effects of the 2% sprays don't last as long because the oil is thinner. There is no need for the effects to last more than 15 minutes.