K-factor (fire protection)

In fire protection engineering, the K-factor formula is used to calculate the discharge rate from a nozzle. Spray Nozzles can be fire sprinklers or water mist nozzles, hose reel nozzles, water monitors and deluge fire system nozzles.

K-Factors calculated in Metric units;

The flow rate of a nozzle is given by ${\displaystyle q=K{\sqrt {p}}}$,[1][2] where q is the flow rate in litres per minute ( l/m ), p is the pressure at the nozzle in Bar and K is the K-factor is given in units of ${\displaystyle (l/m)/{\sqrt {\text{bar}}}}$.

K-Factors have also been calculated and published in US units of PSI and GPM. Within the United States, only US measurements (PSI, and US-Gallons per minute) are used.

Care should be exercised not to intermix K-factors from Metric and Imperial/US units as the resulting factors are not equivalent or interchangeable.