This is a little misleading because a pressure of 30PSI is really needed to get water to boil at 250?F/121?C. A 15PSI Pressure Cookers should really be labelled 15PSI ABOVE AMBIENT PRESSURE and because the atmosphere at sea level is 14.7PSI, then at sea level a 15PSI Pressure Cooker will only reach 29.7PSI and a temperature of just below 250?F/121?C (about 248?F/120?C).
The higher you are, the less effective the Pressure Cooker will be and the longer you will have to sterilise for. At 30PSI a minimum of 15 minutes is required for sterilisation, so at sea level a 15PSI Pressure Cooker requires a little longer than 15 minutes and higher altitudes will require longer.Smiley