Their presence in e-liquids is a primary source, but they may potentially be generated by glycerol (VG) and propylene glycol (PG) when heated to produce aerosols
But in the 19th century, change came, and people started to use cigarettes
In addition to the carry-on baggage, you are allowed to carry the following additional item in the cabin which can go under the seat in front of you: Briefcase/suitcase Laptop bag A small handbag, purse or equivalent A small backpack or diaper bag In addition to the extra item above, you are also allowed to carry the following items in the cabin (subject to security regulations): Cash, important documents, jewelry Camera, laptop An overcoat wrap or blanket A reasonable amount of reading material Umbrella Helping aid for mobility impaired passengers such as a walking stick or crutches Collapsible baby stroller Infant & child food (in reasonable quantity) Liquids Passengers are allowed to carry only small amounts of liquid items in their carry-on baggage, packed in individual containers of no more than 100 ml in volume
But overall, it's a great read
A sample lighting plan is illustrated below