Type A testing involves fire outside the duct. The test
furnace is raised to operating temperatures of 1000oC with
the specimen suspended within. The duct passes through
the dedicated penetration seal where various measurements
and observations are used to determine its suitability and
In this test no fire passes through the duct. The duct is tested for leakage, integrity and the rise in temperature where the duct is insulated. The temperature is measured by up to 80 thermocouples inside the ducting. This determines the kitchen extract insulation value.
Type B involves fire inside the duct. There is an opening in the duct within the furnace which allows the fire to pass through the duct unimpeded. A fan connected to the duct extracts hot furnace gas at a velocity of 3 m/s at up to 500pa negative pressure exposing the internal skin to the full fire conditions. The duct is tested for leakage, integrity and the rise in temperature where the duct is insulated. For this Type B test up to 80 thermocouples are mounted outside the furnace determining the smoke insulation valu.