When a 7.1-magnitude earthquake bucked through the Mexican states of Puebla and Morelos on Sept. 19, 2017, it caused the walls and foundations of schools, apartments and offices a hundred miles away in Mexico City to tremble and, in some cases, topple. Residents watched the buildings teeter and knew they needed to leave immediately.

Thousands of miles away, alerts flickered on in the security-response offices of Airbnb, which now operates three hubs—Annapolis, Md; Capetown, South Africa; and Singapore—to monitor intelligence reports of global disasters. As news reports of the Puebla earthquake rolled in, the disaster-response team deployed a process they call “hitting the button,” activating the Airbnb Open Homes network. The home-sharing tourism company, usually aimed at helping visitors enjoy a weekend away, had converted its infrastructure into an evacuee-housing network.

Across Mexico City, Airbnb hosts received the Open Homes alert, letting them know they were near the disaster zone and asking them if they’d like to volunteer to shelter evacuees from the earthquake. About14,500 hosts and guests received the notification, enabling communication for those trying to find temporary housing outside the rubble of the catastrophe zone. It was the first time the Open Homes network had been activated in Mexico. Eighty one hosts signed up to house evacuees.

Kellie Bentz, head of Airbnb’s disaster-relief efforts.

Kellie Bentz pilots these relief efforts for Airbnb, using the platform’s infrastructure to connect hosts who want to help people in need. “In a disaster, there is a 72-hour window when media is super high and people are trying to take action,” Bentz told From Day One. “This falls into the bucket of donating in kind, which is volunteering your time and space.” To date, Airbnb Open Homes has helped people from 61 countries and housed nearly 25,000 people.

The seeds of the Open Homes program were planted in the wake of Hurricane Sandy in 2012, when Brooklyn-based Michelle (“Shell”) Martinez invited neighbors from flood-damaged New York City neighborhoods including Dumbo, the Rockaways,and the Lower East Side, to camp out in her 6,000-sq.-ft. loft on higher ground. Airbnb sent out an urgent notification about the offer to its network in Brooklyn, and soon it was Martinez’s email inbox that flooded. “Half of it was other hosts saying, ‘How do we do this? My house is empty too,’” recalls Shell (who has since used the Airbnb platform in controversial ways).

As wave after wave of storm refugees navigated dark streets to arrive at Martinez’s apartment, Airbnb engineers in San Francisco worked around the clock to recode the platform for something it had never done before: make apartments available for free to those in need.

The impromptu program that lodged 20 storm refugees and FEMA workers on day beds in Martinez’s apartment has since grown into Airbnb’s multi-country disaster-response network, Open Homes, which Bentz sees as a natural pivot for social good. Bentz cut her teeth on disaster response after Hurricane Katrina, when she founded a relief program called Hands On New Orleans, and later as the leader of global-crisis management at Target.

In her role at Airbnb, she expected to focus on the escalating intensity and number of climate-change-related disasters. But she has been surprised to see that the program has a part to play in other kinds of emergencies, including mass-casualty events. Her most powerful memory is of the Pulse Nightclub shooting in 2016 in Orlando. Working with JetBlue, Uber and the Florida Department of Emergency Management, Airbnb set up at the airport in Miami as friends and family of victims, mostly from the Dominican Republic and Puerto Rico, flew in to visit loved ones in the hospital or to recover remains. “Most people who showed up at the airport that day didn’t think about where they were going to stay. They just got on a plane,” recalls Bentz. “It’s much more than providing that roof; it’s in a moment that they need something and they don’t have to think about it.”

Bentz works with other shared-economy companies like Lyft and Uber to understand how they can use their own platforms to connect people who want to help with those in need. She coaches them to make sure tech companies understand the issue before creating a solution. “The key for businesses to think about is not, ‘What is the solution I think the community needs?’ It’s what do you have to offer and where are you meeting a local need, versus trying to fit a square peg in a round hole just to do something good,” she says.

The Open Homes platform has since extended beyond disaster relief to include refugees from mass- migration movements and medical stays, so families and patients can easily access hospitals that aren’t close to home. “I think it’s wonderful and amazing and I get chills,” Martinez says of how big the program has grown. “But I’m also not surprised. This is who people are: always looking for ways to contribute and ways to help each other out. If you make it available and you make it easy, then we want to do our part.”

Emily Ludolph is a senior editor at 99U and an alum of TED Conferences and Vassar College. She has published in the New York Times, the Atlantic, Narratively, Artsy, 99U, Quartz, and Design Observer