Sperm is an indispensable substance for human reproduction and is a mature male reproductive cell. In fact, sperm are very fragile, and the survival time of sperm after the semen is dried will be very short, about 3~5 minutes only, because after the semen is dried, the sperm lose the protection of semen and will die soon. The survival time of sperm after ejaculation depends on the humidity, temperature, sperm quality and other factors of the surrounding environment. If it is in a humid and cold environment, the survival time may be longer, around 30-60 minutes. If you want to preserve sperm for a long time, you can also use liquid nitrogen for freezing, which can preserve sperm for up to 10 years. After the sperm leaves the body and dries up the semen with a tissue, then the sperm has lost the environment where it can live, so it only has a few minutes of survival time, and it is impossible for such sperm to make a person pregnant. However, under normal circumstances, if the male ejaculates in the female reproductive tract, then the sperm can survive for up to 72 hours because the temperature and humidity in the female body is suitable for the sperm to survive. This is why it is possible to conceive even if a woman does not have intercourse during ovulation. The sperm will die quickly in a dry environment because there is no moisture to protect them after drying, so women do not have to worry about getting pregnant after touching toilet paper with semen on it.