If you ever wonder why there is steam coming out of a New York City manhole. Here's you're answer to that question.
Steam provides mainly heat and hot water to many of the city's residential and office high-rise buildings. It is use as both cost effective and efficient than any other systems for heating tall buildings in New York City.
Steam is also use for sterilizing equipment in some hospitals.
Con Edison, which is the city's utility company that provides the service, will sometimes erect tall orange and white "steam stacks" over the manholes (or "steam box") in order to relieve the steam pressure that is building up underneath the street.
This is to help prevent a blowout such as the one that took place near Grand Central Terminal in the summer of 2007, which killed one person and injured several others.
Some section of the city's steam system range in age from 50 to 100 years old.
ConEd's website has an entire page, which tells the history of steam generation in New York City.
