Breaking in to cars it happens every where and the nearer you are to Marseille the worse it is, I could tell stories of break ins which have all been to cars, also happened a lot around Bleu and Verdon popular climbing areas. Also happens in UK and isnt confined to just campers so no more a risk than driving.
Gas well its one of those urban myths.
Their statement by the The Royal College of Anaesthetists is shown
here. Have a read and judge for yourself.
Despite the increasing numbers of reports of people being gassed in
motor-homes or commercial trucks in France, and the warning put
out by the Foreign Office for travellers to be aware of this danger, this
College remains of the view that this is a myth.
It is the view of the College that it would not be possible to render
someone unconscious by blowing ether, chloroform or any of the
currently used volatile anaesthetic agents, through the window of a
motor-home without their knowledge, even if they were sleeping at
the time. Ether is an extremely pungent agent and a relatively weak
anaesthetic by modern standards and has a very irritant affect on
the air passages, causing coughing and sometimes vomiting. It takes
some time to reach unconsciousness, even if given by direct application
to the face on a cloth, and the concentration needed by some
sort of spray administered directly into a room would be enormous.
The smell hangs around for days and would be obvious to anyone the
next day. Even the more powerful modern volatile agents would need
to be delivered in tankerloads of carrier gas or by a large compressor.
Potential agents, such as the one used by the Russians in the Moscow
siege are few in number and difficult to obtain. Moreover, these drugs
would be too expensive for the average thief to use.
The other important point to remember is that general anaesthetics
are potentially very dangerous, which is why they are only administered
in the UK by doctors who have undergone many years of postgraduate
training in the subject and who remain with the unconscious
patient throughout the anaesthetic. Unsupervised patients are likely
to die from obstruction of the airway by their tongues falling back. In
the Moscow seige approximately 20% of the people died, many probably
from airway obstruction directly related to the agent used.
If there was a totally safe, odourless, potent, cheap anaesthetic agent
available to thieves for this purpose it is likely the medical profession
would know about it and be investigating its use in anaesthetic
practice.