You can get it seems a portable catalytic heater that is flame failure safe, lack of oxygen in the atmosphere safe and also co2 in the atmosphere safe. All these sensors kick in before a co2 alarm does. They also recommend a degree of ventilation ie keep 2 windows 1/2 open and switch off at bed time. £100 +gas 7 kg. INCOMING Taxi for Phil.
It seems to act in the same principle as a Flue,ie air in and out. On the WWW they are popular on sea going boats all over the world and some say they are fine with the windows open about an inch. Others a bit more and others closed. Im on a Norman full of drafts not the space shuttle and I am trying to reduce the risk in a practical way , ie good practice. Ive checked the death rates for condensation on a boat and found it quite low.[:) Sorry if it sounds sarcastic.
If you dunk a Digestive in tea you create an undrinkable cuppa and a missing biscuit. Certain biscuits were designed with condensation in mind, Rich Tea for one, shortbread can handle a bit of damp but to beat an eberspacher you probably need Weetabix.