It took Chinese-American artist Yang Yi five years to complete a mission he set for himself.

On the eve of the 15th anniversary of 9/11, he unveiled it in a solo exhibition at the Chinatown Soup Gallery in New York.

On display are five colossal paintings featuring portraits of all 343 firefighters and paramedics of the New York City Fire Department (FDNY) who lost their lives at Ground Zero after the terrorist attacks of 9/11.

Images of debris, survivors, the American flag flying above the wreckage, and rescuers in various stages of response, create a collage of the events of the city's most difficult day.

Each of the five paintings has its own theme: The dark moment - buildings collapsing; Racing against the clock-rescuing; United we stand-rising from ashes; Sorrow in hearts-salute to the heroes; and Healing and stride forward-God bless America. Together they comprise the work titled First Responders.

"This body of work is both a commemoration and celebration of the American spirit embodied by all New Yorkers whose response to the events of that day will forever mark our national memory," the exhibit's brochure reads.

Artist Yang Yi, 59, came to the US from China in 1995 after winning numerous national awards in China.

Yang, who knew little English, at first made a living by drawing caricatures and portraits for tourists in New York City.

At the time of the terrorist attacks, Yang was drawing portraits at a shopping mall in upstate New York.

He said he will never forget how many people came to him with photos of loved ones who had lost their lives, asking him to create portraits.

In 2010, Yang was driving past a fire station near his house in Flushing when he noticed a mural with pictures of New York and names of victims.

"I had been wondering, as an immigrant artist, what could I do for the US, what could I do to benefit the world rather than my art itself," Yang said.

He decided to paint a tribute of his own - portraits of all the FDNY heroes who sacrificed their lives on 9/11.

He soon learned that it wasn't going to be as easy as he thought. There were so many names and faces, the composition was hard to think through; and as an immigrant knowing very little English, research was difficult.

"Collecting materials was such a painful process for me. The 9/11 National Museum wasn't open yet, so I could only collect material from archives and the internet bit by bit," Yang said.

He took three months to sketch the work before putting brush to canvas.

With no studio, Yang worked in his small apartment. Since each of the five canvasses was 2 meters tall and 1.5 meters wide, he had to keep them stacked on top of each other while working on one at a time.