Half Life: the period of time it takes for the amount of a substance undergoing decay to decrease by halfThe way to compute the replacement rate required to maintain a constant volume with a given half-life is `r = ln(2) / h` where ln is natural log, h is the half life and r is the replacement rate required to maintain a steady state. So, in order to maintain a given volume of oil with a half life of three days and a continuous rate of replenishment, the effective daily rate must be ln(2) / 3 or 23.1% of the total steady state volume. Some rates for reference: `Half Life Replacement Rate` ` 2 ` ` ` ` ` ` ` `34.7%` ` 3 ` ` ` ` ` ` ` `23.1%` ` 4 ` ` ` ` ` ` ` `17.3%` ` 5 ` ` ` ` ` ` ` `13.9%` ` 6 ` ` ` ` ` ` ` `11.6%` |