Safety stops are a recommended procedure at the end of every dive to allow some extra dissolved gases to escape your tissues before exiting the water completely. It is done at 15 feet and it is a must to complete it at 3 minutes or over.
Bubbling is controlled by the difference between the tissue tension and the ambient pressure - however off-gassing is controlled by the difference between the tissue tension and the inspired inert gas partial pressure. This difference, which is is known as the inert gas gradient, determines the amount of off-gassing. If this tissue compartment has a 5 minute half-time then the tissue will go 50% of the way from the current tissue tension to the inspired inert gas pressure in 5 mins
So here are a 10 scuba tips to remember for your 3 minute safety stop.