Team Works

Smoke control fire safety: smoke vents, IFG, public-access building compliance

Three regulatory frameworks structure the analysis: obligations arising from labour law, the type W ERP classification, and the ITGH 25 category.

1 m² of smoke vent per 100 m² of floor area: this IT 246 ratio is not a target but a regulatory minimum, which many older installations no longer meet after several years of operation. For the thermal engineer, smoke ventilation is not just another HVAC item: it is the only package where a 15% undersizing blocks the safety commission and freezes the building’s opening. Kytom has applied IT 246 (decree of 22 March 2004) since 2006, with NF EN 12101-2 smoke vents, 400 °C/2h NF EN 12101-3 fans and category A SSI control, cross-referencing the type W ERP regulation, ITGH 25 and the Labour Code (article R4216-30). The teams integrate roof smoke vents, air inlets and compartmentation (EI 60 doors, IT 247) on floor plates averaging 850 m², up to high-rise (IGH) configurations above 50 m.

Smoke ventilation in offices falls under three complementary frameworks, each with its own triggering thresholds.

Labour Code, Title I Book II: article R4216-30 requires the treatment of windowless or basement premises, and articles R4216-1 to R4216-34 set out the requirements for exits and evacuation in non-ERP commercial buildings.
Type W ERP regulation (offices receiving the public above 100 people): provisions DF 1 to DF 11 apply to circulations longer than 30 m and to enclosed staircases.
ITGH 25 (high-rise buildings, lowest floor of the top level above 50 m): systematic mechanical smoke ventilation, compartments of 750 m² maximum, dedicated fire-resistant ducts.

The IT 246 technical instruction sets the calculation rules: a useful smoke vent area (SUE) at least equal to 1/100 of the ground floor area for natural smoke ventilation, and a flow rate of 1 m³/s per m² for mechanical ventilation. In type W ERP, sizing is set at a minimum on this floor value, then adjusted according to the floor plate configuration and ceiling height, with systematic verification of the CSTB Technical Approvals of the products installed.

Our reading differs from common practice on one specific point. The professional consensus treats natural smoke ventilation as a default option as soon as it is technically permitted. In practice, on our recent operations below 400 m², installing motorised smoke vents adds 25 to 40 EUR/m² with no operational gain compared to compliant facade openings. Below a 300 m² floor plate, or on a single ground floor with no circulation constraint, smoke ventilation via facade openings is sufficient. Conversely, in basements and in horizontal circulations longer than 30 m, natural ventilation is excluded by IT 246: only mechanical ventilation is permitted.

What smoke vent ratio should be planned for a 1,000 m² type W ERP?

IT 246 sets a minimum of 1 m² of useful smoke vent area (SUE) per 100 m² of floor for natural smoke ventilation. In practice, smoke vent sizing is set at a minimum on this floor value, then adjusted according to the floor plate configuration, ceiling height and the opinion of the safety commission. The choice between natural and mechanical depends on the geometry: circulations longer than 30 m and basements require mechanical ventilation.