The JNYSM includes a pharmacy in a concession stand and nursing stations built from scratch. Kenneth Sanchez, head of facilities for the Javits Center, said that one of the hardest things to find were the 50 mobile showers his team amassed from as far away as Georgia. The vendors had to unlock their businesses to fill the orders, he said.

Already, supplies like the modular walls Javits used are growing scarce, as convention centers around the country have started to build their own emergency hospitals. “Whereas three weeks ago, you could have called someone and said, ‘Give me a thousand walls tomorrow,’ ” Steel said, “now they’ll say, ‘I’m sorry. They’re in Chicago. They’re in Las Vegas. They’re in Houston.’ ”

The expectation is that FEMA will reimburse the Javits Center for their costs. As a “public benefit corporation” that provides a service to the state by bringing in people who spend money on restaurants and hotels, the facility doesn’t rely on taxpayer dollars. It simply looks to break even each year.

Down another corridor strange commands floated into the hallway: “Forward, back, down, up,” a medic told a National Guardsman who was wearing an N95 mask under what looked like the hood for a hazmat suit. Soldiers were lined up — six feet apart — for the chance to bow and shake like they were at a concert thrashing in a mosh pit. It was a simulation to test the fit of their masks and mimic a confined environment.