Required Fire Flow
Calculate the water flow required for a firefighting system, Q = area × application rate, multiplying the operating area (m²) by the required application density (L/min per m²). The result, in L/min, is the minimum flow the sprinkler or spray system must deliver over the most unfavourable area to control the fire. The application rate depends on the occupancy's hazard class — the higher the fire load and combustibility, the higher the density required by codes (NBR/NFPA). It is the basis of hydraulic design and water reserve. Enter the area and the application rate.
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Required fire flow
To control a fire, an automatic sprinkler system must apply water over the burning area at a sufficient density — dumping a lot of water on a single spot is useless; the whole design operating area must be covered at the right rate. The total required flow is Q = area × application rate, multiplying the design operating area (the most unfavorable portion assumed to be burning, in m²) by the required application density (L/min per m²). The result, in L/min, is the minimum flow the system (pump, piping, and reservoir) must deliver. The density and the operating area come from the occupancy's hazard class in the standards (NBR 10897, the Brazilian sprinkler standard, and NFPA 13): light hazard (offices, schools) uses low densities (~4–5 mm/min, i.e. L/min/m²) over smaller areas; extra hazard (flammable liquid warehouses, plastics) demands much higher densities over wide areas. This flow is the basis for sizing the fire pump and the water reserve (together with the required duration). Undersizing means failing to control the fire; this is the calculation that connects the expected fire severity to the hydraulic infrastructure. Enter the operating area and the application rate.
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Sprinkler Flow (K-Factor)
Calculate the flow of an automatic sprinkler, Q = K × √P, from the head's K-factor and the pressure at the sprinkler P. The result, in L/min, is the water discharged by the sprinkler at a given pressure — the basis of the hydraulic design of sprinkler systems, which must ensure enough flow and application density over the most unfavourable operating area. The K-factor characterizes the orifice (the larger it is, the more flow at the same pressure). Mind the units of K and P, which must be consistent. Enter the K-factor and the pressure.
Specific Fire Load
Calculate the specific fire load of a space, q = (mass × LHV) ÷ area, dividing the total energy of the combustible materials (mass × lower heating value) by the floor area. The result, in MJ/m², is the heat that would be released per unit area if all the material burned — the parameter that classifies a building's fire risk and sets protection requirements (fire resistance, exits, sprinklers) in fire codes. The higher the fire load, the more severe the potential fire. Enter the fuel mass, the heating value and the area.
Building Population
Estimate a building's population, Pop = (area per floor × number of floors) ÷ density, from the usable area per floor (m²), the number of floors and the occupancy density (m² per person). The result, in people, is the total population to be served by the vertical transport — the starting point of elevator traffic analysis. Occupancy density varies with use: ~10 m²/person in dense offices, ~15-20 m²/person in standard offices, with specific values for hotels and residences. Compared with the elevators' handling capacity, it tells whether the system is adequate. Enter the area per floor, the number of floors and the density.
Smoke Plume Mass Flow
Calculate the mass flow of a fire's smoke plume by the Heskestad correlation, ṁ = 0.071·Q̇_c^(1/3)·z^(5/3), from the convective part of the heat release rate Q̇_c (kW) and the height above the fire base z (m). The result, in kg/s, is the amount of hot gases and smoke rising and accumulating, governing the design of smoke control and exhaust systems (mechanical or natural) that keep a smoke-free layer for safe evacuation. The flow grows strongly with height. Enter the convective heat fraction and the height.
Refrigerant Mass Flow
Compute the refrigerant mass flow needed in a cycle, ṁ = refrigerating capacity / refrigerating effect, dividing the desired cooling load (kW) by the specific refrigerating effect (kJ/kg, the enthalpy absorbed per kilo at the evaporator). It is how much refrigerant must circulate per second to meet the demand — the basis for sizing the compressor, the piping and the system gas charge. Enter the refrigerating capacity and the refrigerating effect.
Emergency Exit Width
Calculate the required width of an emergency exit, W = (population ÷ unit capacity) × 0.55, dividing the population to be discharged by the capacity of people per exit unit and multiplying by one unit's width (0.55 m). The result, in metres, sizes doors, corridors, stairs and ramps of escape routes by the exit-unit criterion of fire safety codes. The capacity per unit varies with the type of exit (door, stair, ramp) and the occupancy. Enter the population and the capacity per exit unit.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.