Did You Know....

1. Did you know that bacteria are too heavy to float in the air?  They will fall down to the surface in still air. I'd expect the same thing happens with particulate matter in the atmosphere.
2. Did you know that most bacteria cannot survive dessication? They dry, they die.
3. Did you know that "constant humidity salts" will maintain a constant humidity in a closed container?  Great for humidors.  Just make a saturated solution of the salt, add more of the salt so some undissolved salt remains.  This mixture will suck enough moisture out of the air in the container to keep the humidity in the container constant.  A saturated solution of table salt will maintain a constant humidity of around 72%. See Table on link.  These salts can be ordered  through a chemical supply site.
4. Did you know that Legionnaire's disease has been found in hot water tanks set at 120F?  The only way to make sure you don't get Legionnaire's disease is to set you hot water heater's temperature to 130F.  See CDC and the survival temperature table on Wikipedia under Prevention. Notice the 5km range survival of these bacteria.  Humid conditions.. i.e. not dry.