Depends how good the vapour pen is and also were you buy it from , i spent £50 on my new vapour pen and i have not had one problem so i would say no their not dangerous in my opinion. Any how if you were to buy the disposable vapour pens ( the cheap one's that cost around £5-£10 ) their have been a few cases were they have exploded in some ones hand or mouth. were i live their was recently some one who had one blew up in their hand they got 3rd degree burns to their face and hands. so what im saying is Dont buy they cheap disposable vapour pens