Fortunately carbon monoxide being lighter than air rises and since there was no upper floor then no one would have been exposed to this danger in the roofspace.
Thatch fires were common (and still are!) and so various remedies were employed including occasionally applying limewash especially in towns where buildings were close together.
Open hall fires were damped down and covered over at night with a large clay pot called a "couvre feu" [fire cover] and this term later became modified to become "curfew" which we now understand as meaning a time by which everyone must be off the streets. I note that The Weald & Downland Open Air Museum now employ these devices as an overnight fire safety precaution device in open hall buildings where fires are burned on the floor hearth.