As a shooting player you may choose to pocket an obvious object ball and also discontinue a turn at the table by declaring "safety" in advance. If you intend to play safe by pocketing an obvious object ball, then prior to the shot, you must declare a "safety" to the opponent. If this is not done, and one of your object balls is pocketed, you will be required to shoot again, while any ball pocketed on a safety shot remains pocketed. All fouls and other rules apply to a safety shot.
For more detailed information on 8-ball game visit rules page.
Let's play safe! :)