I have an older home which is not equipped with conventional air duct. This makes it certainly hard to heat in the winter. In the kitchen, we’ve installed a compact, natural gas heater. This gas furnace is a ventless, single-phase heater. Because it is ventless, it creates an oily film on the windows in the kitchen. I have a pair of antique French doors which each have twelve small windows. These windows are time-consuming and aggravating to clean. In the summer, I rarely need to worry about them. During the winter, they are forever cloudy and in need of a thorough scrubbing. Because the gas furnace is a single-phase unit, it blasts heat at maximum capacity machine it achieves the temperature control setting. It then shuts down and cools itself by blowing cool air. The constant on and off cycling results in unpleasant temperature swings. The ventless gas furnace is also certainly temperamental and requires constant filter cleaning. At least once per week, I need to remove the several filters and meticulously clean them. If there is any debris clogging the filters, the warning light on the machine starts blinking red, and when this happens, the gas furnace will no longer shutdown. It keeps running on maximum capacity, and I worry that it might overheat. Overheating could disfigure the gas furnace or even present a safety hazard. Once a year, the filter cleaning is not satisfactory, and I need to take the gas furnace apart and clean it with high pressure air. The pressurized air removes any buildup of dust. Unfortunately, this dust then fills our kitchen. I should perform this job in the summer, as a proactive strategy, when I can open the windows. Instead, I always wait until the gas furnace refuses to operate properly, in the middle of the winter.