A rendering shows one possible location for an emergency ventilation plant underneath East 37th Street between Park and Madison avenues. View Full Caption Metropolitan Transportation Authority

MIDTOWN — The MTA will tear up parts of Park Avenue in Midtown over several years to build a ventilation system for the subway — a crucial project that will help bring fresh air into the underground tunnels in case of fires or other emergencies, officials said.

The plan is to build the ventilation plant under Park Avenue somewhere between East 36th and East 39th streets, making it possible to get fresh air flowing into the 4/5/6 tunnels on the Lexington Avenue line in the event of an emergency, according to MTA representatives, who made a presentation at a public meeting at Mount Sinai Beth Israel on Thursday.

Those tunnels currently have no emergency mechanical ventilation system to pump out smoke if fire breaks out according to a scoping document for the project.

When the city built its original subway tunnel system in the 1920s none had mechanical ventilation plants, but most stretches of tunnels have been retrofitted to make emergency ventilation possible, according the project description.

But the portion of Lexington Avenue line tunnels between East 33rd Street and Grand Central are still without a modern emergency airflow system, the document says.

A 1994 study of ventilation at 242 segments of tunnel in the New York City transit system found the stretch between 33rd Street and Grand Central to be number five in terms of priority, according to the agency.

But it wasn't until the 2015-2019 capital program made funds available for the work that it became feasible, said Emil Dul, an environmental engineer at the MTA.

While many residents at the meeting agreed that the work is necessary, some questioned whether the project was imperative if it was only happening now, two decades after the 1994 study.

Concerns were also raised about whether safety measures would be in place to protect air quality in the neighborhood above ground, in the event the ventilation system were to pump out smoke, or even poison gas.

"This is not required work," said Murray Hill resident Parce Ainsworth. "This seems like a use-it-or-lose-it state funds situation."

Representatives of the MTA did not immediately respond to community comment, but they said the remarks on Thursday will be logged as part of the public review process.

Construction on the ventilation plant will take about four and a half years to complete, and will likely require tearing up portions of Park Avenue, with all the traffic detours associated with major roadwork, according to the document.

When possible the MTA uses vacant properties to build above-ground ventilation plants, but found nothing suitable in the area of the Lexington Avenue line, according to a scoping document for the project.

The agency has drafted a list of possible locations for the plant, which include:

►Underneath the northbound lane of Park Avenue between East 36th and East 37th streets, between East 37th and East 38th streets, or between East 38th and East 39th streets.

►Unerneath the divider separating Park Avenue between East 39th and East 40th streets.

►Underneath the divider separating Park Avenue between East 37th and East 38th streets.

► Underground, between Lexington and Park avenues or between Park and Madison avenues, at East 36th, East 38th or East 39th Street.

Locations east of Park Avenue would cost an estimated $93.9 million, while locations west of Park Avenue would run the agency an estimated $96 million, and a plant built directly underneath Park Avenue would cost about $85.5 million, the agency said.

The public has until July 1 to submit comments to the MTA, which may be mailed to Emil F. Dul, Principal Environmental Engineer, MTA New York City Transit, 2 Broadway, Fifth Floor, New York, NY 10004.