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The general prohibition:
Irregular benefit: Biblically, it is only forbidden to benefit from Chametz in the regular fashion of benefit. However, Rabbinically, even irregular benefit of Chametz is forbidden. Nonetheless, if one needs to benefit from the Chametz for medicinal purposes, the Sages permitted irregular benefit to be done if one does not own the Chametz, such as he borrows it from a gentile. This applies even if the illness does not involve danger.
Benefiting from burnt or inedible Chametz: All Chametz which has reached the state of being inedible even to a dog prior to the 6th hour on Erev Pesach, is allowed to be benefited from on Pesach. However, Chametz which was burnt after the 6th hour on Erev Pesach, is prohibited in benefit, and thus its heat, flame, and charcoal/ash cannot be benefited from until after Pesach.
Benefiting from Taaruvos Chametz in food products: See Halacha 1H regarding the eating and owning prohibition relevant to edible mixtures that contain Chametz. The general rule is as follows: All Chametz mixtures which are permitted to be owned are likewise permitted in benefit.
Benefiting from Taaruvos Chametz in non-food products: All non-food products that contain Chametz ingredients which have disintegrated into the product, are permitted to be owned and benefited from over Pesach. See Chapter 6 Halacha 4 for the full details of this subject!
Benefiting from Matzah Ashira; Chametz Nuksha; etc: See Halacha 1E-F!
When does Chametz become prohibited in benefit?
It is Biblically forbidden to benefit from Chametz starting from midday [the start of the 7th hour of the day] of the 14th and onwards, throughout the seven days of Pesach. The Sages added one more hour towards this prohibition, and thus it is forbidden to benefit from Chametz starting from the start of the 6th hour from sunrise and onwards. This applies even if the Chametz does not belong to him. [Starting from this time, it is forbidden to benefit from even Rabbinically forbidden forms of Chametz, such as Chametz Nuksha or Rabbinical Taaruvos Chametz.] However, it is permitted to receive pleasure from all forms of Chametz until the beginning of the 6th hour of the day, even though it is prohibited to be eaten starting from the 5th hour. Thus, one may sell Chametz to a gentile throughout the 5th hour of the day even if the gentile will not be able to consume the entire amount prior to the beginning of Pesach. Likewise, one may feed the Chametz to animals and birds throughout the 5th hour, so long as one supervises that all the Chametz is eaten.
Starting from the 6th hour on Erev Pesach, it is forbidden to receive benefit from any Chametz.
What actions are forbidden due to benefit starting from the 6th hour?
Disowning: It is forbidden to disown the Chametz after the 6th hour on Erev Pesach [by declaring it hefker and placing it in a public area, and rather one must destroy any Chametz that he still has not removed from his home].
Feeding animals: It is forbidden to feed Chametz to even a wild, disowned, animal. It goes without saying that is forbidden to feed Chametz to animals that he owns. Furthermore, it is forbidden to give one’s animal to a gentile caretaker during Pesach, if one knows for certain that the caretaker will feed Chametz to the animal.
Smelling baking Chametz: From the 6th hour and onwards, it is forbidden to smell [for pleasure] the Chametz of a gentile that is baking. [Thus, one may not smell the Chametz of a gentile bakery. See Q&A!]
Cooking water in a Chametz pot for non-drinking purposes: It is permitted on Pesach to occasionally cook water in a Chametz pot for the sake of using the water for laundry, or bathing, and the like of non-drinking purposes. This however may not be done on a steady basis, unless the pot is not designated to be used for cooking food. If the pot is used for food, it is to be hidden away with all the other Chametz vessels and only used on occasion.
Doing business with Chametz on Pesach: See Halacha 11!
Feeding a gentile employee Chametz on Pesach: See Halacha 12!
May one feed ownerless Chametz to an animal?
If one’s animals only eat Chametz foods, what should he do with them over Pesach?
In such a case, one is to sell the animals to a gentile before Pesach, having them included in the Mechiras Chametz contract.
May one eat meat/eggs or drink milk from animals/chicken that were fed Chametz?
See Chapter 6 Halacha 9!
Does one have to move away during Pesach if he lives near a gentile bakery and will inevitably smell the Chametz?
No. However, he may not intend to receive pleasure from the smell
May one pass by a bakery even though he will inevitably smell the Chametz?
One may do so, so long as he has no intention to smell the Chametz. However, if there is an alternative route available, it is best for one to use it and circumvent the bakery.
May one barbecue hotdogs or marshmallows over the flame used to burn the Chametz?
The custom is not to do so even when burning the Chametz prior to the 6th hour on Erev Pesach.
 Admur 431:2
The source for prohibiting benefiting from Chametz? The verse [which describes the eating prohibition] states “Lo Yochal: Do not bring yourself to eat.” This means to say that there is no permissibility to make use of the Chametz in a way that will lead one to eat a food, even a permitted food. It is thus forbidden to receive benefit from the Chametz [such as by selling or exchanging the Chametz], as general benefits lead one to eat food, as one buys food with the money he makes from the sale of Chametz. [Admur 431:2]
 Admur 443:3
 Admur 466:4; See Rambam Yesodei Hatorah 5:8
 Admur 445:11; 442:24 “Any item that is permitted to be owned on Pesach may likewise be benefited from”; Michaber 445:2; Pesachim 21b
“When destroying the Chametz prior to the 6th hour, [being] that the Chametz is still permitted in benefit, one does not need to make a separate flame [from that of his cooking oven] for the Chametz, and he rather may burn it in his cooking oven, and use its heat to cook with, as well as he may get all other types of benefit from it. Furthermore, even after the 6th hour one may continue to benefit from the heat derived from the Chametz if the Chametz has already been burned, before the 6th hour, to the state of being inedible even to a dog. Nevertheless, the custom is to burn it separately [from ones cooking oven, and not benefit from it,] even when burning it prior to the 6th hour.”
 Admur 445:8 “When one burns his Chametz after the 6th hour, [being] that the Chametz is [now] prohibited in benefit, one needs to burn it individually, and may not place it in his fire used to bake or cook on. Furthermore, one may not use its light or warm oneself up from it or receive any other forms of benefit from it similar to these. Furthermore, even the charcoal/ash of the Chametz is prohibited in benefit.”
Benefiting from the non-Chametz ash: The charcoal and ash of the wood used to burn the Chametz are permitted in benefit. Thus, if one recognizes the wood ash and knows for certain that the ash is from the wood and not from the Chametz [then it may be benefited from]. If the Chametz and wood ash mixed together to the point that it is no longer recognizable as to which is which, then the entire mixture is forbidden in benefit [until after Pesach] [Furthermore] the charcoal and ash of the Chametz is not batul even in a 1000:1 ratio of wood ash to Chametz ash. The reason for this is because the Chametz ash [is considered a Davar Sheyeish Lo Matirin, being that it] becomes permitted after Pesach without needing to nullify it, and the rule is that any item which will become permitted [without needing to nullify it] is not nullified even within a 1000 against it. [Admur ibid]
May one use the Chametz ash to do the Mitzvah of covering the blood of a slaughtered bird or Chayah? It is permitted to cover the blood of a bird: chayah with the ash of the burned Chametz. The reason for this is because Mitzvos were not given to benefit from. Meaning that the Mitzvos were not given to the Jews for their fulfillment to be pleasurable for them. Rather they were given as a yolk on their necks. [Admur ibid]
What if one transgressed and used the Chametz to help fuel the fire used to cook with? See Admur 445:9-10; “A Semicha aid for learning the laws of Pesach” chapter 445!
 Admur 442:24; M”A 442:7 regarding the Tiraka; Chok Yaakov 447:13 and 18; Implication of Terumos Hadeshen 113
 Admur 431:2
The source: [Just as it is prohibited to eat Chametz starting from midday of Erev Pesach, as explained in Halacha 3, so too it is forbidden to benefit from the Chametz from that time and on, as] the sages had received [an oral tradition] that the Chametz prohibition on the 14th is similar to the prohibition of Chametz on the 7 days of Pesach, and being that throughout the 7 days of Pesach, Chametz is Biblically prohibited even in benefit, so too from midday of the 14th and onwards the Chametz is prohibited even in benefit. [Admur ibid]
 How to calculate the hours: The two hours are calculated in accordance to the number of minutes that exist within the 12 hours of daylight within one’s area. Thus, [both in areas where the daylight hours are less than 60 minutes per hour, and] in places where the daylight hours is more than 60 minutes per hour, one nevertheless follows the Zmaniyos amount of minutes that exist within the hour. [Admur 443:4]
Other opinions and Time of need: Since there are opinions who hold that these hours are [no more than] 60 minutes each, as is the case by average days [as since these two hours are only Rabbinical therefore one may be lenient], therefore, one may rely on this opinion in a case of great loss to sell his Chametz up to 60 minutes before midday, even if the Zmaniyos hours contain more than 60 minutes. [Admur 443:4]
therefore one may be lenient]. [brought in Admur 443:4]
 Admur 443:4; 459:10; Siddur in Hilchos Kerias Shema; GR”A
Other opinions: Some Poskim rule we calculate the hours starting from Alos Hashachar. [M”B 443:8 in name of many Poskim; Admur 89:1 regarding Davening; M”A 233:3; Peri Chadash 89; Levush 233, 267] Regarding the sale of Chametz, some Poskim conclude that certainly one is to initially be stringent like those opinions who hold that it is calculated from dawn. [Rav Avraham Chayim Naah in Yagdil Torah 6:2604]
 Implication of Admur 443:1; See Chok Yaakov 443:3; Chemed Moshe 443:1; Kaf Hachaim 443:7; See however Olas Shabbos 443:1; Chok Yosef 443:2; Kaf Hachaim 443:4
 Admur 443:1
The reason: It is permitted to receive pleasure from all Chametz, even Chametz which is Biblically prohibited on Pesach, until the beginning of the 6th hour, as the Sages did not want to decree against getting pleasure from the Chametz during the 5th hour. [Admur ibid]
 Admur ibid
 Admur 443:2
The reason one must supervise: One must be careful to supervise the animals, to make sure that they do not hide the Chametz somewhere in his property and thus cause him to transgress Baal Yiraeh after the time of the prohibition begins. Thus, whatever is left over from their eating should be destroyed. The same applies when feeding the animals prior to the 5th hour. [Admur ibid]
 Admur 443:3
 Admur ibid; Mishneh Pesachim 21a regarding selling
 The reason: This is forbidden due to two reasons: a) As by doing so one receives benefit from the Chametz; b) As once the time of Issur has arrived, one must destroy it from the world, and selling it does not suffice.
 Admur ibid
The reason: As once the benefit prohibition has arrived, the Chametz is no longer considered his and one must thus destroy it from the world. Giving it away as a present does not suffice.
Other opinions: Some Poskim allow giving the Chametz to a gentile even after midday [Avnei Nezer O.C. 528; See also Doveiv Meisharim 1:119; Piskeiy Teshuvos 448:31]
 Admur ibid
Other opinions: Some Poskim allow disowning the Chametz even after midday [Avnei Nezer O.C. 528; See also Doveiv Meisharim 1:119; Piskeiy Teshuvos 448:31]
 The reason: As one receives benefit by fulfilling his desire to satiate the animals hunger. [M”B 448:28]
 Admur 450:18
 Admur 443:3 in parentheses; Biur Halacha 443 “Afilu”; See Shach Y.D. 108:27
Other opinions: Some Poskim rule it is always permitted to smell forbidden foods that are not designated for smelling even if they are forbidden in benefit. [Rashba; Beis Yosef; Mordechai brought in Shach 108:27; See Rama 155:3 “It goes without saying that one may spray Yayin Nesech on fire [for the sake of smelling it] even if one is healthy, as a smell is meaningless”]
 Admur 450:13
 M”B 448:28; Beis Yosef
 Shaar Hakolel 4 Seder Mechiras Chametz of Admur
 Glosses of Maharsham 447:8; Piskeiy Teshuvos 443:2
 See Maharsham ibid and Piskeiy Teshuvos ibid