Natural smoke ventilation concerns the atrium proper. The adjoining rooms and thoroughfares leading into the atrium must be fitted with mechanical smoke ventilation.
Natural smoke ventilation of an atrium features (for covered atriums only):
In the upper part:
Smoke ventilators or openings with a total aerodynamic area equal to: 1% of the base section with a minimum of 2m2, if the atrium: only has M1 fire rated furniture or if the building has a highest floor height of 8m in relation to the bottom of the atrium. 1/15 of the base section in other cases.
In the lower air supply part:
Free area equal to that of the vents, which may be: openings in building facades, access doors leading to the outside or ventilated passages, air inlet/outlet openings.
A control unit (NFS 61-938).
If the atrium is in a public building, NF marking is mandatory, recommended in all other cases.
It must be:
servo-controlled by a fire detection system
coupled with a manual control unit at the service access point or at the central control station.