I remember a long time ago when I went to visit my aunt with my parents.
It was a crazy experience because when my aunt didn’t answer the door and we saw her car was there, we panicked.
My father ended up finding a spare house key under one of the stones in the front. When we found my aunt passed out in the bed not waking up, my father shouted for me to open up all the windows and fast! I did exactly as he said because I knew this was serious even though I didn’t know why I had to open the windows at first. There was a breeze through the house after all the windows and doors were open and the fresh air certainly was refreshing. My mother called the police to get my aunt to the hospital. My father told me he knew that it was carbon monoxide that made my aunt sick. He said he knew because he had checked her heating system before and it was on its way out. He said that thing probably overheated and caused a crack to form in the heat exchanger. When that happens, the HVAC system is basically toast because the fix costs just as much as a new HVAC upgrade. It was confirmed that carbon monoxide was the culprit through medical tests and fortunately my aunt survived. She probably would have died if we didn’t act so quickly to open the windows to get the carbon monoxide poison out of the house. If we would have arrived even 30 minutes too late, she could have died also.