IL is a twin wall insulated pre-fabricated domestic gas vent manufactured in the UK by SFL. It is designed for naturally aspirated domestic gas fired appliances with a draught hood/ diverter and where the chimney is required to operate under negative pressure, dry conditions and the flue gas temperatures must not exceed 250°C.


  • Available in 100 and 125 internal diameter.
  • Aluminium liner and a zalutite outer case.
  • 6mm air gap insulation.
  • Vertical seams are rolled and securely locked.
  • Inner and outer casing are joined at one end only meaning the inner liner is free to expand as the temperature changes in the vent.
  • Suitable for internal and external applications.
  • Suitable for appliances rated up to 75kW
  • Not suitable for condensing and positive pressure applications.
  • Twist-lock jointing system
  • Range of flue boxes available.


Internal Diameter 100mm 125mm
External Diameter 114mm 140mm


  • Manufactured and certified to BS EN 1856-1
  • Tested to BS EN 1856 with designation T250 N1 D Vm L11030 0(50)

  Filename Format  
Gas Flue Box Brochure Gas Flue Box Brochure .PDF
IL Brochure IL Brochure .PDF
IL Product Summary IL Product Summary .PDF