What is the first step when using a fire extinguisher as per P.A.S.S.?

The first step when using a fire extinguisher, according to the P.A.S.S. method, is to pull the pin. This action is crucial because it releases the safety mechanism and enables the extinguisher to be activated. Without pulling the pin, the extinguisher cannot function, as it prevents accidental discharge. Once the pin is pulled, the user can then proceed to aim at the base of the fire, squeeze the handle, and sweep the nozzle to effectively put out the flames. Understanding this sequence is vital for ensuring quick and effective responses in fire emergencies, particularly in environments like construction sites where fire hazards may be present.