870. Smoking on Tisha b'Av

124:14 One should not go for a walk in the marketplace on Tisha b'Av in order that he should not to come to frivolity or enjoyment.  Some authorities prohibit smoking tobacco on Tisha b'Av, while others permit it after midday in the privacy of one's own home. (Editor's note: this halacha does not reflect the permissibility or impermissibility of smoking in light of modern medical information on the subject. Consult your rabbi.)

124:15 Regarding acts of labor, the practice is that any work that would take some time is prohibited on Tisha b'Av night and the next day until midday, even if it is not a professional-level job.  Something that does not take much time, like lighting candles or tying knots, is permitted. (The rules for writing might be the same as on chol hamoed - Bi'ur Halacha 554:22 s.v. al y'dei akum.) After midday, one may perform all forms of labor. The practice is to prohibit business transactions before midday and to permit them after midday. A pious person should be strict the whole day, both when it comes to labor and to business transactions, so that he will not be distracted from mourning.  One is permitted to have any manner of labor performed for him by a non-Jew and if one is faced with the possibility of a financial loss, he is permitted even to do the work himself. It would be preferable to have cows milked by a non-Jew but if this is not possible, one may do it himself.