All flight attendants and a few pax...?
What if ...
If you assume all flight attendants were standing and most pax seated at the time you would expect a relatively light gas or vapor being the cause of this. Light enough to spread relatively fast along the ceiling of the whole of the cabin. Would be interesting to know if the affected pax were or had been standing too. Those that were not, might give an idea about the origin location.
Until now I have never read an incident or accident report that gave the seating and standing locations of POB in such cases. Descriptions are all quite vague. Would be nice if the DTSB would produce a more detailed report in this case, locations and all. Especially because of the fact that in this specific case all ccw were affected and only a few pax.
Smoke, vapor, smell, particles, dust ... Sometimes they give the color of the smoke. You generally dont get more detail than that. Certainly not enough of a starting point to start separating these cases by their various natures and causes.
Was reading some reports the last few days. In one case white smoke was thought to be caused by condensation after riser ducts failed. The other case was white smoke thought to be dust descending from psu panels that dropped when the ac hit an obstruction during a rwy excursion. Thats were the detail ends.
In one report they stated that the cause was not a fire ... "Because the smoke was white" ... Well, uh, ...