It’s 110 flights of stairs — or 2,220 steps. And it symbolizes the route taken by 343 members of the New York Fire Department killed at the World Trade Center on Sept. 11, 2001. The National Fallen Firefighters Foundation Annual 9/11 Memorial Stair Climb honors those who selflessly gave their lives that day so others might live.

Each NFFF 9/11 Memorial Stair Climb completes the fallen firefighters’ journey. These events help sustain NFFF counseling and support programs for all families of firefighters who succumb to line-of-duty deaths, according to a press release.

This year the 9/11 Memorial Stair Climb will be held at Salt River Fields at Talking Stick on Saturday, Sept. 10. Onsite registration begins at 5 p.m. and opening ceremony at 6:30 p.m. The climb goes from 7–9 p.m.

The 9/11 Memorial Stair Climbs are held throughout September, with the majority taking place on Sept. 10 or Sept. 11, a press release stated. Members of the public join community first responders at stadiums, speedways, high schools, tall office buildings, even the Red Rocks amphitheater in Colorado and Lambeau Field in Wisconsin. Each carries a photograph of a firefighter who died on 9/11.

Participants can also register as virtual climbers by climbing, walking, running, or biking indoors or outdoors between Sept. 11 and Oct. 31. Virtual participants will receive a toolkit with badges for the heroes who died and access to a digital bell to ring when they complete the event.

It is important to remember that responders and survivors still feel the health effects more than 20 years later. Researchers have identified more than 60 types of cancer and other conditions linked to toxic air and materials. An additional 5,380 responders and survivors have since died due to the exposure.