Each volunteer is called a
unit (as in, a crew of one) and is assigned a unit number that starts with a neighborhood code, followed by a
serial number for that neighborhood (e.g., "Q-120" means "Queens unit number 120"). In some areas there may be periods where coverage is not strong enough, for example on a summer weekend. When this happens, coordinators may assign an on-call rotation. The rotation may still respond from their houses, or they may stay at the garage through their shift. In such periods, Hatzalah functions closer to a typical EMS crew setup, though the dispatchers may still seek non-on-call members to respond, and there will still often be a non-ambulance responder as first dispatched, even if that responder starts from the base.
Response times Hatzalah's model provides for rapid
first responder response times. Each Hatzalah neighborhood's response time varies. For example, in
Borough Park, Brooklyn, daytime response in life-threatening emergency are between 1–2 minutes, and nighttime response times are 5–6 minutes. However, following implementation of Truck-1 (night on-call crews) the nighttime response in Borough Park was shortened significantly. In Israel, the response time is under 3 minutes.
Organization Hatzalah is not a single organization. Each chapter operates autonomously, or, in some cases, with varying levels of affiliation with neighboring Hatzalah chapters and under a central association. In New York City, there are usually two or three members who are "coordinators", managing all operational aspects of the chapter. The New York City-area Hatzalah is formally called Chevra Hatzalah of New York. It combines dispatch and some other functions for over a dozen neighborhood chapters, which each have their own fund-raising, management, garages, ambulances, and assigned members. Together, the combined
New York State branches have grown to become the largest all-volunteer ambulance system in the United States. == Legal status ==