Necessities of Existence

Most of the time I take air for granted.  Yet without a regular supply of air death is inevitable.  There is a limit of how much foreign gas and other pollutants can be present before air is dangerous.  Bitter cold can make air dangerous to breathe.  When we drove east this fall we encountered smoky air that made me worry about proceeding on our track, and smoke inhalation is a greater cause of death than fire itself.  So I am grateful for the air that I usually ignore.