Amidst his discussion of Bedikat Hames (the search for Hames that one conducts the night before Erev Pesah), the Shulhan Aruch (Orah Haim 432) writes that before one begins the search, he recites the Beracha, "Asher Kideshanu Be'misvotav Ve'sivanu Al Bi'ur Hames." The text of this Beracha makes reference to the "Bi'ur," the elimination of the Hames, rather than the search for Hames, because the search functions merely as the means whereby we begin to fulfill the Misva of Bi'ur. In order to eliminate the Hames in our home, we must first thoroughly search the home and collect all the Hames. Needless to say, if a person only searched his home but did not destroy the Hames he discovered, the search was futile. Therefore, since the search merely facilitates the Bi'ur, the Beracha we recite before beginning the search makes reference to the Bi'ur, which is the ultimate purpose and goal of the search. The reason why we recite the Beracha prior to beginning the search, rather than prior to the Bi'ur, is because the search constitutes the beginning of the Bi'ur process, thus warranting the recitation of a Beracha.
If a person owns multiple properties that he must search for Hames, such as if he owns a summer home or a store, he recites a single Beracha and then searches all the properties. Even if they are at a distance from one another, he nevertheless recites a single Beracha, searches the first property, and then immediately proceeds to search the second property. If, however, the two properties are very distant from one another such as if a person owns a home in Brooklyn and another in Deal then it is preferable to have in mind when reciting the Beracha that it applies only to the first property he searches. He then recites a new Beracha before beginning the search in the second property.
If one's family members or guests will be assisting in the search, they do not each need to recite an individual Beracha. Rather, they should all assemble before the search and the head of the household recites the Beracha on their behalf. If they did not hear the Beracha, they may nevertheless participate in the search and do not recite individual Berachot. If the head of the household commissions somebody else to search the home, and he does not participate at all, then the person performing the search should recite the Beracha. It should be noted, however, that it is preferable to personally involve oneself in the search, at least to some extent, given the Halachic principle of "Misva Bo Yoter Mi'beshluho," meaning, that it is a greater Misva to personally perform a Misva than to commission somebody else to do so on one's behalf.
One should not speak from the moment he recites the Beracha until after he completes the search, except in matters related to the search. For example, when the need arises one may ask somebody during the search to bring him new batteries for the flashlight. Speaking in other matters, however, is forbidden throughout the search. It is therefore advisable to disconnect one's telephone and turn off his cellular phone during the search. If after reciting the Beracha but before beginning the search one spoke in matters unrelated to the search, he must repeat the Beracha. If he spoke after he had begun the search, he does not repeat the Beracha.
Summary: Before one begins the search for Hames he recites the Beracha "Asher Kideshanu Be'misvotav Ve'sivanu Al Bi'ur Hames." A single Beracha suffices for all properties a person searches on that night, unless one home is very far away from the first, in which case he recites a separate Beracha on the second home. If several people search the home together, only one person recites the Beracha. If a person commissions somebody else to search his home, and he does not participate at all, the person who performs the search recites the Beracha. One should not speak in matters unrelated to the search from the moment he recites the Beracha until he completes the search.
