samuel23:
Sperm samples collected into a sterile container may remain alive for many hours, but their fertilising capability drops dramatically after 60 minutes mainly due to a major reduction in their ability to swim rapidly(motility).
Sperm exposed to room air on clothing, bed linen, toilet seats or the like, lose motility very rapidly. Once the semen dries out, the sperm are usually dead. Drying is, of course, dependant on ambient temperature and humidity.
The maximum time sperm have shown motility and viability outside the human body is about 72 hours, but survival depends on a both a suitably high temperature and humidity. In practice, these criteria are rarely met.
The nutrients contained within semen are necessary for the survival of spermatozoa. Without the semen , sperm die rapidly. Sperm removed from semen and placed in water, only survive for minutes due to the hypotonic nature of water ie water has a lower osmotic pressure than semen. The end result is that the spermatozoa swell up and explode.
All in all, sperm are not designed to survive outside the human body.