Test Requirements - Non-Grease
ISO 6944 (1985) is the accepted Standard for the USA and Canada.
The purpose of ISO 6944 (1985) is to measure the ability of a ductwork system to resist the spread of fire from one fire compartment to another without the aid of fire or smoke dampers.
It should be noted that the test relates to a complete ductwork installation and, therefore, joints, supports, and the fire stopping through the furnace wall all form an integral part of the test.
- ISO 6944 (1985) Fire Resistance Tests – Ventilation Ducts.
Requirements of ISO 6944 (1985)
The fire rating of ventilation ductwork shall, according to the Standard, be expressed in minutes of duration of heating until failure occurs according to one or more of the following criteria:
Criteria of Failure:
1. Stability: Stability failure shall be deemed to have occurred in duct Type A within the furnace and in duct Types A and B outside the furnace when the duct collapses and no longer fulfils its intended function.
2. Insulation: Insulation failure shall be deemed to have occurred when the temperature rise above initial ambient temperature on the surface of the test specimen outside the furnace exceeds either:
- 284°F as an average value or
- 356°F as a maximum value.
For kitchen extract duct Type A, these temperature rise limits also apply to the inside surface of the duct within the furnace.
3. Integrity: The presence and formation of cracks, holes, or other openings outside the furnace through which flames or hot gases can pass shall constitute integrity failure.
Definitions of Types A and B Fire Exposure
The testing standard differentiates between types of fire exposure; two classifications apply as detailed below.