I have just rented a place for the winter and they have supplied me with a Calor gas portable heater. I am a little worried about using it as I have never done so before. I worry about emissions, mainly carbon monoxide. They tell me everyone uses them , it's the cheapest form of heating and not to worry. I would like to hear from those of you who use them. What do you think? They tell me to make sure the room is properly ventilated. What does 'properly ventilated' actually mean?