A fire marshal, in the United States and Canada, is often a member of a fire department but may be part of a building department or a separate department altogether.
An average human red blood cell is approximately 5 microns in diameter. The average diameter of human hair is roughly 0.0035 inches in diameter, which is equivalent to 75 microns. The abbreviation micron was initially used to distinguish the units of a tool used to measure small distances, also called a micrometer.
That said, a micron is a pretty big distance for a lot of things. It's still a thousand times bigger than a nanometer. Refer to the hand/football field again for a nanometer. This is the scale of viruses and certain computer components.