While the newly constructed decontamination unit at the New York Downtown Hospital on Gold Street blends into the façade of the hospital’s emergency room, appearing to be a simple loading dock for ambulances, the hospital says it is in fact the city’s largest facility to counteract the deadly effects of chemical, biological, and nuclear weapons.

The new “decon unit” was built as part of the $25 million Lehman Brothers Emergency Room that opened last September, a project catalyzed by the terrorist attacks of September, 11, 2001, after which the hospital treated about 1,500 victims.

Before the construction of the new facility, New York Downtown Hospital’s tiny decontamination unit could handle about 20 patients an hour. “With the amount of people who came to the hospital on 9/11, we needed to reassess things,” the interim chief of the department of emergency medicine at the hospital, Dr. Antonio Dajer, said. The new unit can treat between 500 and 1,000 patients an hour.

To formulate a design, the hospital sent a task force to Shaare Zedek Medical Center in Jerusalem, where they learned that the key to a functional “decon unit” is simplicity.

“You have to attend to large numbers of patients quickly,” Dr. Najer said. “You don’t want a lot of bells and whistles.”

Because water is the single greatest antidote to contamination, according to Dr. Najer, the hospital installed 25 high-power showerheads that jut down from the roof of the semi-outdoor enclosure.

The open-air blueprint, based on the Shaare Zedek Medical Center, serves several important purposes, according to the hospital’s administrative director of the emergency department, Peter From.

Handcuffed by downtown Manhattan space constraints, the outdoor design ensured the hospital could construct a large facility while also guaranteeing that in the aftermath of a terrorist attack, contaminated patients would remain outside of the sterile hospital.

Unlike the sultry climate of Jerusalem, frigid New York winters aren’t conducive to outdoor showers, so the architectural firm hired by the hospital, Norman Rosenfeld Architects LLC, designed a custom heating system. The shower water is warmed by a 1,000-gallon tank that is separate from the hospital’s water supply, ensuring a constant supply of heated water. Gas-powered heaters are scattered along the roof of the facility.

The unit also has several outlets that can pump “medical air” into the self-contained suits that physicians wear while treating contaminated patients.

“It’s arguably the most technologically advanced decontamination unit in the world,” Dr. Najer said.

Citigroup has been the largest donor, giving $400,000 of the nearly $1 million needed to construct the New York Downtown Hospital’s decontamination unit.

The unit has other functions as well, according to the hospital’s assistant vice president of public affairs and marketing, Vanessa Warner. In the case of plane crash, it could be used to clean hazardous jet fuels off of victims, and it could double as a car wash for ambulances.