Is it permissible to buy chicken from a factory that produces pork?
Question

There is a factory that produces chicken and pork. What is the ruling on eating the chicken from this factory – is it halal?
Praise be to Allah.Firstly:
In order for chicken and other meats to be halal, there are two conditions:
The first condition:
The slaughterer must be qualified, meaning that he should be a Muslim or one of the People of the Book, i.e., a Jew or a Christian). Meat slaughtered by an idol-worshipper, atheist or apostate is not permissible.
The second condition:
The chicken should be slaughtered in a place for slaughter, and it should not be killed by means of an electric shock, beating or drowning in water, because that is prohibited in the verse in which Allah, may He be exalted, says (interpretation of the meaning):
{Prohibited to you are dead animals, blood, the flesh of swine, and that which has been dedicated to other than Allah, and [those animals] killed by strangling or by a violent blow or by a head-long fall or by the goring of horns, and those from which a wild animal has eaten, except what you [are able to] slaughter [before its death], and those which are sacrificed on stone altars} [al-Ma’idah 5:3].
Al-Hajjawi said in al-Iqna‘ (4/316): There are several conditions that are stipulated for slaughter:
1.. The slaughterer should be qualified, which means that he should be of sound mind and intending to slaughter the animal in the proper manner. He should be a Muslim or one of the People of the Book (i.e., a Jew or a Christian), even if he is one whose people are in a state of war with the Muslims or one of the Christians of Banu Taghlib; male or female, free or slave, even if he or she is junub, menstruating, bleeding following childbirth or blind, of good character or otherwise.
It is more appropriate if the slaughterer is a Muslim rather than a Jew or a Christian.
Meat is not permissible if it is slaughtered by a person one of whose parents is a disbeliever who is not one of the People of the Book. Meat is also not permissible if it is slaughtered by an apostate, even if he joined the religion of the People of the Book; or if it is slaughtered by a Zoroastrian, an idol worshipper or a heretic. The same applies to the Druze, the Isma‘ilis and the Nusayris of Syria…
2.. The tool used for slaughter should be sharp, cutting and penetrating by virtue of its sharpness, not its weight, whether it is made of iron, stone, wood, reeds, bone or anything else, except teeth and nails…
3.. The throat – meaning the windpipe – and the oesophagus – which is the passage for food and drink – must be cut, but if they are cut completely, that is better.
The more correct view is that it is not stipulated to cut the veins on both sides of the throat, but it is better to cut them. End quote.
Secondly
If the factory produces pork products, and also produces chicken products, the matter is subject to further discussion:
1.. If it produces whole chickens or parts such as legs and breasts, and the one in charge of slaughter is a Muslim, or a Jew or a Christian, then there is nothing wrong with buying chicken from them, because it is most likely that the chicken is not mixed with the pork, and the tools used for slaughter are kept separate.
2.. But if it produces ground chicken meat or canned chicken meat, if it is known that the same equipment is used to produce pork products, then it is haram to eat this chicken, because it is impure as a result of using equipment that is contaminated with pork, unless it is possible to wash it and purify it, in which case the chicken is permissible.
Undoubtedly it is better to completely avoid chicken that is produced in factories like this which also produce pork products, especially if we cannot find out what they really do in the factory, and the supervising authorities are not certain about their slaughtering procedures and the extent to which they adhere to Islamic rulings on slaughter.
The scholars of the Permanent Committee were asked:
Some restaurants grill beef on the same hotplate as pork. Is it permissible to eat that meat? Similarly, they use the same knife to cut the meat.
They replied: It is not permissible to eat beef that is grilled on the same hotplate as pork. The same applies to the knife."(Fatawa al-Lajnah ad-Da’imah  22/285).
They were also asked:
Sometimes I eat in the student restaurant. Of course I avoid haram foods, but sometimes I order fried potato or fried eggs, and one time I saw the woman who cooks the food frying eggs in the same oil with meat. I do not know what the meat was, but I am almost certain that it was pork. Is it haram to eat the eggs and potatoes?
They replied: If you are certain that some food is fried in the same ghee or oil in which pork was fried before, then do not eat it, otherwise it is permissible for you to eat it."(Fatawa al-Lajnah ad-Da’imah 22/283).
For more information, please see the answers to questions no. 148426  and 62839  .
And Allah knows best.