I have a entirely odd effect that regularly happens to the mirror in my powder room throughout the time, this happens every single time my central heating & A/C idea turns on and kicks into gear; When the air conditioning or the heating comes on, my bathroom mirror ends up fogging up! It is kind of like what you see when you are in a boiling shower with the door closed for a long time. The mirror does this typically! When it first started happening I particularly thought I was losing my mind or something! I knew me or my beloved husbandy did not just take a shower. It stumpfest for quite a while and embarrassingly took about a month to figure it out, however I figured it out on Monday that I noticed the air vents started pumping out massive volumes of the heat or the air conditioning. It never did this before. The underlying reason for it was also absolutely odd. It eventually turned out that there was something else very important going on. It seemed there was some kind of steam coming directly out of the air vent! Every one of us took our time and eventually figured this could be a bigger issue so every one of us called the local heating & A/C supplier to ask for their professional opinion. They sent out one of their certified heating & A/C specialists and they told us the outside air was combining with the air from the central heating & AC system. This is what was causing the steam!