Nozzle Reaction

What Is Nozzle Reaction?

Nozzle reaction is the backward force (measured in pounds of push) exerted against a hose crew according to Newton's third law, calculated as $NR = 1.57 imes d^2 imes NP$ for smooth-bore nozzles and $NR = 0.0505 imes Q imes \sqrt{NP}$ for fog nozzles.

Why Nozzle Reaction Matters on the Fireground

High nozzle reaction rapidly fatigues interior attack crews. A 2½-inch line flowing 250 GPM at 50 PSI generates about 125 lbs of backward thrust, requiring proper stance and backup firefighters to control the line safely.

Relevant NFPA Standards

• NFPA 1010: Standard on Professional Qualifications for Firefighters
• NFPA 1550: Standard for Emergency Responder Health and Safety

Field Procedures & Tactical Steps

1. Position the nozzle operator with feet shoulder-width apart, leaning forward into the reaction force.
2. Pin the hose line against the hip or leg to transfer backward force down into the ground.
3. Position a backup firefighter 2 to 3 feet behind the nozzle operator to absorb line weight and reaction.
4. Open and close the nozzle bail slowly to avoid sudden reaction spikes.
5. Use smooth-bore nozzles (50 PSI NP) when lower nozzle reaction is needed for heavy GPM delivery.

Common Context & Application

Evaluated by nozzle teams advancing attack lines (1¾-inch and 2½-inch) during interior structural suppression.

Frequently Asked Questions about Nozzle Reaction