I'm buying a heat alarm for my older Vermont Casting wood stove that comes with either a probe sensor that requires a 1/8" hole drilled into a double wall chimney OR a surface mount sensor. My main concern is forgetting the damper and allowing the temps to get way too high. After 25 yrs of operation, we've been safe but have had some close calls. Since sensors are now available, I'd like to be safe. I fully understand that they will have two different temperatures and i can adjust to that but which one is better? If I get the probe for the chimney, it will interfere with cleaning the chimney and probably will get gucked up with residue which may affect the readings but in the event of a chimney fire, it would provide the best alert. If I get the surface sensor, I would attach it to the stove and the readings should be very close to the thermometer that I use now but I'm not sure if it will alert me in the event of a chimney fire. Can't get both unless i buy 2 alarms. Appreciate your suggestions?