CFM to L/s Converter

Converting between US HVAC airflow ratings (CFM) and SI ventilation specifications (L/s) for international projects, equipment integration, and code compliance.

European fan curves published by manufacturers such as Ziehl-Abegg, Ebm-papst, Nicotra-Gadda, and Comefri plot airflow in L/s against static pressure in Pa; when these fans are specified for US projects, the conversion to CFM (and inches water column for pressure) is required at every step of the design package.

ASHRAE Standard 62.1 (US) specifies outdoor air and total air flow rates in CFM/ft² or CFM/person, while the European equivalent EN 16798 specifies the same in L/s/person or L/s/m² — a building designed for 1,000 occupants at 20 CFM/person (US office) = 20,000 CFM = 9,438 L/s, which converts to roughly 9.4 L/s/person — close to the EN 16798-1 default of 10 L/s/person for office spaces.

Smoke control and stairwell pressurization systems per NFPA 92 (US) use CFM, while EN 12101-6 (Europe) uses m³/s — the conversion is required when applying European smoke-control engineering to US high-rise buildings or vice versa.

Laboratory fume hood face velocity specification is 80–120 fpm per ASHRAE 110 (US) and 0.4–0.6 m/s per EN 14175 (Europe) — the same physical airflow, different units; with the hood open at 18 inches (0.457 m) wide and 28 inches (0.711 m) tall (a 4-foot hood), the face area is 0.325 m² × 0.5 m/s = 0.163 m³/s = 163 L/s = 344 CFM through the hood opening, requiring equal exhaust capacity from the building exhaust system.

Engine intake and turbo boost specifications in automotive engineering use CFM in the US aftermarket (a K&N Typhoon intake rated 550 CFM) and L/s or m³/min in OEM European service documentation (the same physical flow being 259 L/s).

Welding fume extraction, paint booth ventilation, and other industrial exhaust systems appear in either unit system depending on the equipment manufacturer, with OSHA permissible exposure limits (PELs) given in ppm and the ventilation flow required to maintain compliance given in CFM (US) or L/s (EU/IFA).

Mine ventilation main fan ratings per MSHA (US) are in CFM (a 250,000 CFM main fan for an underground mine is large but not exceptional) while the same equipment from a European or Australian manufacturer would be specified in m³/s — boundary fans and booster fans must be specified in both units when a global mining company operates in mixed jurisdictions.

Data center hot-aisle/cold-aisle containment design uses CFM per rack in US practice (a 10 kW rack at typical 1,500 CFM supply) and L/s per rack in European practice (the same rack at 708 L/s); the conversion factor 0.4719 L/s per CFM appears in every CRAC unit selection and CFD model.

Tunnel ventilation for road and rail tunnels per NFPA 502 (US) is in CFM, while PIARC (World Road Association) and European standards use m³/s — a longitudinal ventilation system for a 2 km road tunnel might require 1,500,000 m³/h = 416,667 L/s = 882,857 CFM of fresh air supply during normal operation.