Electronic cigarettes and other corresponding products may not be packed in cargo hold luggage.
You may not charge these batteries onboard a flight. Passengers must obey the airline's instructions regarding their use during the flight.
The change to the mode of transport is based on the international instructions regarding transport of dangerous goods by air (ICAO Technical Instructions for the Safe Transport of Dangerous Goods by Air, Edition 2015-2016, Addendum No.1).
The change is due to fires caused by electronic cigarettes in aircraft cargo holds. Detecting and putting out possible fires in the cargo hold is more difficult than in the passenger compartment, where the aviation staff have access to fire extinguishing equipment.
Source: Press release by the Finnish Transport Safety Agency (Trafi) 2 July 2015