A: All gas appliances need air to burn properly (ie combust the gas). If you are planning to install a 'flueless heater', such as an LPG cabinet heater, it will take its air directly from the area it is heating and will discharge its products of combustion back into the area.
For this reason, flueless heaters need to be installed in well-ventilated areas, and must NOT be installed in bedrooms, bathrooms or any area that could be used for sleeping.
Using calculations, your gasfitter can work out the correct flueless gas heater for the size of the room.
He or she can also recommend the best type of heater for your home, depending on how well ventilated it is.