Separation between livestock and people only came in the very late 1800s or the early 1900s. Only the rich could afford draft horses to pull their plow. Thick smoke billows out of the doors as he enters from a hard day spent in the fields. No, it's just the open fire that is kept burning day and night in the center of the living quarters at the back of the house. This large open fire sends smoke throughout the house.
Smoke is a good thing.
It cleanses the air of bacteria. It also dries the crops, which are stored in the loft high in the rafters of the house. The smoke cures meat, hanging from hooks above the living area. The smoke drives away insects. That's why in the 1800s and before, people normally slept sitting up.