Fresno City Fire. "10 - 18" call

[CZ]

Heard a unit being dispatched to a "10 - 18" call, listened for a while but essentially all I heard was that the unit (or units?) had arrived.
What's a "10 - 18" Any ideas?

 

[USAPatriot]

Heard a unit being dispatched to a "10 - 18" call, listened for a while but essentially all I heard was that the unit (or units?) had arrived.
What's a "10 - 18" Any ideas?

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