Hilchos Pesach – 13 / searching for chametz

1. One may nullify his chametz wherever he may be, and the chametz does not need to be in his proximity. If there is concern that he may forget to nullify the chametz, his wife may nullify it on his behalf. But no other person can nullify it on his behalf unless he explicitly appoints that other person as his messenger to nullify his chametz. In this case, the messenger recites this formula: “The chametz of so-and-so shall be nullified wherever it may be” (Shulchan Aruch and Mishnah Berurah 434).

2. A guardian of orphans must search for chametz on their behalf and nullify it (ibid.).