The VFB 120/120 then leaves a maximum 25mm air gap to allow for drainage and maintain ventilation in normal use. In a fire situation the intumescent seal rapidly expands to seal off the air gap and prevent vertical fire spread within the external wall.

The products have undergone extensive fire testing following the principles of BS EN1363-1 and in accordance with ASFP TGD19 (Fire Resistance Test for ‘Open-State’ Cavity Barriers).

The VFB 120/120s are mechanically fixed horizontally within ventilated cavities behind the external wall substrate following the fire compartment line. The VFB 120/120s are used horizontally and can be installed in conjunction with Tenmat NVFB Non-Ventilated Fire Barriers which provide vertical fire separation along fire
compartment party wall lines.