1. A candle that was kindled as one of the Chanukah lights but was then extinguished withinthe time of the mitzvah (i.e., within a half-hour) becomes forbidden and may not be used for any other purpose. Even if that candle was somehow mixed with even a thousand other ordinary candles, they all become forbidden, since the higher status of the Chanukah candle prevents it from being nullified among the majority (Shulchan and Mishnah Berurah 673).
2. However, if the Chanukah-candle was only mixed among the other candles after the eight days of Chanukah passed, in which case it no longer has its higher status, then it is nullified among the majority of mundane candles and they are all permissible for use (ibid.).
