Whether it’s post-masturbation, post-hand job or an accidental orgasm, sperm won’t survive very long if left on the skin or other surfaces (like a towel or toilet seat). Most studies show that the sperm in semen die within 3-5 minutes of time spent outside of a body (meaning not inside a testicle or a vagina), and once that semen is dry the sperm is definitely dead.

Other things that kill sperm almost immediately: water (yep, just plain water), soap, hand sanitizer, chlorine in pools and hot tubs (sorry Glee fans).