Question: Dear Craig, I have read your archives with interest. We have just purchased a home (circa 1979) with two fireplaces that have inserts and systems which circulate water heated by the fire down to the furnace. These water grates are within the masonry chimney. There is a pump to move the water and the furnace fan pushes out the warm air. Our home inspector says that these are unsafe (in Philadelphia suburbs we don't have a lot of wood heat expertise) The current owner uses them all the time. Can you direct me to more information? Answer: Well, they could be safe...if: 1. They are not DIY..that is, if they were made to be boilers. 2. The hookups are correct, and the controls and valves functioning. 3. A pressure relief valve is installed on each one and piped outside or into the basement below. Because of the low water capacity of these heat exchangers, they could easily overheat...which is why the PR valve and controls are so important. Maybe the old homeowner has a plumber/service guy who is familiar with the devices and can assure you of their safety...and also service them when needed.