I inserted my brass key into the door lock.  About nine months previously, I had closed and locked this same door.  My small winter retreat on the Arizona desert had stood shuttered and empty all that time.  As the door swung open, interior air wafted out, smelling dusty and stagnant.  The air was heavy.  Then I sensed a whiff of . . . rotten eggs?  Where could that come from?  I then realized I was smelling hydrogen sulfide.  Looking further, I realized that the water in the "P” trap under the sink had evaporated in the thermal summer heat allowing lethal sewer gas rich in hydrogen sulfide, methane, and other vapors to enter the space and displace oxygen.  Although my small winter retreat was designed for continuous human occupancy and easy to enter and exit, the home’s interior had had poor natural ventilation and had produced a hazardous environment.  My space had become a confined space.  Hazardous confined spaces are everywhere, even in non-work situations.