Orange Steam Funnels Are a New York Symbol. What Are They For?

To quickly establish that a film is set in New York City, a Hollywood director could show the Empire State Building or the Brooklyn Bridge. But often, the chosen symbol is far less majestic: an orange-and-white-striped tube spewing steam over a busy street.

These plumes of hot vapor are as closely linked to the city as yellow taxis, the subway and 24-hour bodegas.

The steam funnels are an appendage of the city’s extensive network of pipes that distribute steam, at high pressure and about 400 degrees Fahrenheit, to office towers and apartment buildings throughout the densest parts of Manhattan.

Created 142 years ago, the steam system is the United States’s oldest and, with 105 miles of pipes, its largest. The utility company Consolidated Edison uses those pipes, most of which are buried beneath the city’s streets, to supply steam for heating, cooling and other commercial uses like dry cleaning.

But now and then, here and there, one of the pipes springs a leak and the escaping steam billows up through the nearest manhole.

A large leak can produce enough fog to startle pedestrians and obscure the view of drivers. Martin Scorsese famously captured that effect in the opening scene of “Taxi Driver” nearly 50 years ago.

To prevent any harm, Con Edison routinely sends crews out to cover the source of the rising steam with a 10-foot-tall plastic tube — Con Edison calls them “stacks” — that funnels the steam away from street level. The funnels, either solid orange or striped, have become totems of New York.

Woody Allen included one that rose from Fifth Avenue in the opening montage of “Manhattan.” In one of the final episodes of HBO’s “Succession,” Kieran Culkin’s character leaves his father’s funeral and walks past one in the middle of East 55th Street.

“Movie producers ask if they can rent them or buy them from us,” said Frank Cuomo, Con Edison’s general manager of steam services. He said one producer had contemplated using dry ice to simulate steam for a shot. But, he cautioned, if you ever see one onscreen in a scene set in Brooklyn or the Bronx, it has to be a fake.

Although some of the commercial steam is produced across the East River, it all ends up in Manhattan.

Con Edison delivers steam to more than 1,500 buildings between the tip of Battery Park, at the southern end of the island, and 96th Street. Demand surges on weekday mornings when superintendents start heating up their buildings for the workday.

Most of the steam is purchased by owners of commercial and residential buildings, including Madison Square Garden, the Chrysler Building and the World Trade Center. The 9/11 Memorial & Museum uses steam to keep its reflecting pools from freezing, Mr. Cuomo said.

The rest goes to hospitals, hotels, schools, churches and museums. They use it for heating water, air conditioning and humidification.

The steam is produced at four plants in Manhattan, one in Brooklyn and one in Queens. The principal source is Con Edison’s massive power plant at the end of 14th Street, near the East River. That plant, which has been in use since 1926, originally burned coal to produce steam and electricity.

The utility pumps copious amounts of city water — the Department of Environmental Protection says Con Edison is one of the five biggest users — into its giant boilers there. Scorching flames turn it to vapor and keep heating that steam to more than 400 degrees Fahrenheit before sending it out around Manhattan.

The pipes are packed into the snarl of infrastructure under the streets that includes water and gas mains, power lines and fiber-optic cables. But the water that often seeps down there after heavy rains is the enemy of the steam system.

If a steam pipe is immersed in water, the steam can cool and turn to water. The pipes contain traps designed to remove the water, but if they fail, disaster can ensue.

That’s what happened in 2007 to an 83-year-old pipe under the intersection of Lexington Avenue and 41st Street, a block from Grand Central Terminal.

Water inside the pipe caused it to burst in what Con Edison described as a “bubble-collapse water hammer.” Simply put, a bubble of steam imploded and two pockets of water slammed into each other, creating a pulse of extremely high pressure that the pipe couldn’t contain.

The rupture created a geyser of brown muck laced with asbestos. One person died and dozens were injured.

That catastrophe spurred Con Edison to adopt technology to help it monitor conditions inside the pipes to avoid a similar explosion, said Hugh Grant, who oversees the steam system for the company.

Although demand for its steam peaked in the 1970s, he said, Con Edison sees a long future for the system as building owners make changes to comply with requirements to reduce greenhouse gas emissions.

Con Edison has identified 1,000 buildings that could switch from oil or natural-gas boilers to steam service at relatively low cost because they are within 250 feet of a steam main, Mr. Grant said. Still, there is the larger matter of Con Edison’s carbon footprint: All of its own boilers are fueled by natural gas.

Con Edison is considering alternatives, including installing an industrial-scale heat pump and switching to lower-carbon fuels like hydrogen and renewable natural gas, Mr. Grant said.

One thing that is unlikely to change any time soon is the frequent appearance of those orange cylinders piping steam away from the Manhattan streetscape — and the curiosity they provoke.

“People always ask what the stacks are all about,” Mr. Cuomo said.