Cut-off fire dampers are used in places where ventilation or air conditioning ducts pass through building partitions, which are elements of fire separation. Under normal conditions, all hatches are open – remain in the waiting position. Fire dampers in the event of a fire, they close in the zone, where a fire was detected, allowing it to be cut off – go to the safety position and protect the remaining zones against the ingress of fire and gases through the ventilation duct system. At the same time, it is possible to operate ventilation and air-conditioning systems in other fire zones.
There are now fire dampers on the market, whose fire resistance was assessed using two different methods. The first is the method, used up to half in the ITB Fire Research Laboratory 1999 year, which was carried out under the so-called "static conditions". Static conditions were assumed as contractual, that on the heated side of the element – in a research furnace, there was an overpressure under the ceiling 20 ± 3 Well, and weather conditions on the unheated side. Two basic criteria were assessed in this study:
• E – fire tightness, tj. time, expressed in full minutes, through which the damper maintains its separating function without:
– appearance on the damper surface or in the mounting partition around the damper flames lasting longer than 10 s,
– formation of gaps on the surface of the damper or in the mounting partition around the damper, which will allow the insertion of a feeler gauge with a width of 25 mm, or which will allow the insertion of a feeler gauge with a width of 6 mm and shift it along the slot by 150 mm,
– inflammation of the cotton-wool tester, handed over by 30 s to any point of the non-heated surface of the tested element.

• I – fire insulation, tj. time, expressed in full minutes, through which the damper maintains its separating function, without bringing up the flap surface on the unheated side, which:
– raises the average temperature more than 140°C above the starting temperature,
– or anywhere increases more than 180°C above the initial temperature.

Two tests of fire resistance of cut-off fire dampers were subjected to
trial items: with the largest and smallest cross-section from a given series of types. The method of incorporation of test elements into the building partition should correspond to real conditions. Due to the lack of pressure difference in front of and behind the closed damper during the fire test, in order to relate the actual conditions to the conditions used in the classification method, in the event of a fire in the building, it was necessary to turn off the ventilation and air conditioning. In this way, the pressure difference between the zone covered by the fire was eliminated, which is cut off by the hatch, and the rest of the ventilation or air conditioning system.

From July 1999 a new method of testing the fire resistance of cut-off fire dampers has been introduced in the Fire Research Laboratory of ITB, which can be conventionally called testing under "dynamic conditions". In this method, the assessment of individual criteria of fire resistance is carried out with a maintained constant pressure difference in front of and behind the closed damper, amounting to 300 Well. The fire test must be preceded by a mechanical test at ambient temperature (similar to testing under static conditions), consisting in carrying out 50 damper opening and closing cycles. The same propulsion system shall be used for the mechanical test, which is actuated by a thermal release during a fire test. After the examination, it works itself out, whether the damper is still locked in the closed position, and that it does not show any mechanical damage, that would affect its operation. If none of the damper elements is damaged, the damper is subjected to a fire test. The assessment of fire resistance of the cut-off fire dampers is performed on the fire test stand. The fire test is performed on the damper with the largest dimensions in a given series of types. The first two minutes from the start of the fire test (the moment of exceeding the temperature of 50 ° C at any measuring point of the test furnace is taken as the beginning) decide about the possibility of further research. Cut-off partition of the tested damper, through which the air flows at a speed set before the start of the test 0,15 ± 0,02 m/s, should close as a result of the thermal release in no longer than 120 s. After the hatch is closed, it takes place, by adjusting the fan speed, setting a negative pressure in the connection conduit in relation to the interior of the furnace at the level 300 ± 15 Well, which should be held until the end of the fire test.

During the fire test in dynamic conditions, the following criteria for fire resistance of the damper are assessed:
• E – fire tightness, tj. time, expressed in full minutes, through which the damper maintains its separating function without:
– appearance on the damper surface or in the mounting partition around the damper flames lasting longer than 10 s,
– formation of gaps on the surface of the damper or in the mounting partition around the damper, which will allow the insertion of a feeler gauge with a width of 25 mm, or which will allow the insertion of a feeler gauge with a width of 6 mm and shift it along the slot by 150 mm,
– inflammation of the cotton-wool tester, handed over by 30 s to any point of the non-heated surface of the tested element, and
– flow rate exceeded by flap leaks, measured with a measuring orifice (5), values 360 m3/hm2 (referred to 20 ° C).

• I – fire insulation, tj. time, expressed in full minutes, through which the damper maintains its separating function, without bringing up the flap surface on the unheated side, which:

– raises the average temperature more than 140°C above the initial average temperature,

– or anywhere increases more than 180°C above the initial average temperature.

• S – smoke tightness, tj. time, expressed in full minutes, through which the damper maintains its separating function without:

– flow rate exceeded by flap leaks, measured with a measuring orifice (5), values 200 m3/hm2 (referred to 20 ° C), this condition must be confirmed at ambient temperature before starting the fire test. The above condition applies to the values ​​measured after 5 min test and therefore the flow rate values ​​measured from the closure of the damper to the end of the 5th minute of the fire test are not taken into account.

The difference of pressure before and after the closed damper during the fire test and measurement of the leakage rate and determination of its limit allowable value, they allow for approval in real conditions, in case of fire, after closing the dampers in the fire zone, the ventilation and air conditioning system worked consistently in the rest of the building. Fire shut-off dampers, despite a developing fire in the isolated fire zone, they protect other zones against fire and gases from getting through the ventilation duct system. This basic difference between the fire dampers with fire resistance confirmed in "dynamic conditions" and the fire dampers with fire resistance confirmed in "static conditions", determines the possibility of using individual dampers in facilities with specific scenarios of the development of events during a fire.