Q. If someone due to contracting Covid lost his sense of smell and finds himself in a hospital room where the smell of the bathroom is obviously present, since other patients avoid it and say so. Can he say a bracha or learn Torah there, since after all he can't smell the stink? If not, if he places next to him a deodorizing block that he also can't smell, would it be permitted?
A. On question 1361 regarding davening and saying brochos when visiting a site next to farms where there is an ever-present odor of cow manure, we wrote; "Mishna Berura (79: 28) and Biur Halacha (ibid.) quoting Chaye Adam, rule that you are not allowed to recite brochos in a refes bokor or animal barn that has a bad smell due to animal excretions.
Mishna Berura (85: 7) prohibits even for a person that can't smell. See similar in Vehaya Machanecha Kadosh (2:2:2); that even if the bad smell does not particularly bother someone, since he is used to it, it is prohibited. (Piskei Teshuvos (79:1).
However, Shvilei Dovid (76: end) is lenient for one that cannot smell or has become used to it, as long as the waste material is not human.
It stands to reason that every individual has his own particular adaptation time period for different smells.
Horav Shlomo Miller suggested that in your case, the visitors should bring with them a can of spray air-freshener or odor eliminating product, and spray the area before reciting a brocho. (See similar in Maharsham 2: 38, Minchas Yitzchoh 8: 9, Shevet Halevi 3: 17, Piskei Teshuvos 79:2). Those spray cans could be used also on Shabbos (Igrois Moshe quoted in 39 Melochos 2: p. 377)."
Similarly, in our present question, Horav Shlomo Miller's Shlit'a opinion is that even if someones smell is affected, he may not daven or learn Torah since the bad smell prohibits davening or saying any words of kedusha regardless of his sensitivity.
However as above, if a deodorant was applied and the bad smell would not be felt by others, it would be permitted.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit'a