Building Materials and Systems and Fire Resistance

Question 1

Explain the purpose of fire dampers.

(4 marks)

Answer 1

Fire dampers are installed where duct work **passes through a compartment **(walls or floors) to seal the space within the duct work in the event of a fire stopping/limiting the spread/movement of fire, smoke and flammable gases to other areas of the building.

• Typically activated by a thermal device at the site of the damper such as a fusible link.
• Differents types
  (i) Intumescent
  (ii) Curtain
  (iii) Multi-blade
• Normally open but in the event of a fire, the damper closes.

Question 2

Explain the difference in design and operation of Curtain and Intumescent Dampers

Answer 2

Curtain
* series of interlocking metal blades, which fold into the top of the damper assembly holding it open for general use.

(i) on activation/detection of fire/smoke the damper releases via a fusible link or thermally activated (~72c).

(ii) Blades decend closing off the space within the duct work, sealing it against smoke and flames.

Damper installation should be in the line of the separating element (wall or floor).

Intumescent
* components which expand in the presence of heat to close the space within the duct work, preventing smoke and flame spread.

• if a cold smoke seal is required an electro-mechanical device is fitted to activate the damper on detection of smoke/fire by the buildings detection system.

Damper installation should be in the line of the separating element (wall or floor).

Question 3

Explain three ways of maintaining the fire resistance of walls and floors penetrated by ventilation ductwork.

Answer 3

(i) Via Fire Dampers
* placed int he plane of the element in question and activated via fusible link or mechanical means in the event of a fire.

• close the internal space within the ductwork maintaining the compartment, preventing the spread of fire and smoke.

(ii) Via Fire Resistant Enclosures
* ductwork is enclosed in a fire resistant enclosure (shaft or riser)

• fire protection to the ductwork is provided by the enclosure.
• compartmentation maintain by fire stopping at the wall or floor penetrations using appropriately tested and approved systems.

(iii) Via Fire Resisting Ductwork
* ductwork is constructed from materials providing the neccessary fire resistance.

• can be metal ducts coated with fire resisting materials (paints or boards).
• fire stopping required at the point where the ductwork passes through the seperating element (penetration seals) paying attention to smoke control and the supporting of the ductwork.

Question 4

Describe the different types of penetration seals used to maintained fire resistance of compartment walls or floors.

Answer 4

(i) Batt and Mastic System
* incoporating appropriate pipe closures where plastic pipes pass through a compartment wall.

(ii) Linear Joint Seal
* required between fire resisting elements eg junction between a floor and a wall.

eg elastomeric expansion joint strip.

(iii) Small Cavity Barrier
* installed between two leaves of masonary to prevent passage of fire in an unseen or inaccessible space.

(iv) Large Cavity Barrier
* used to subdivide the space in a roof void or beneath a raise floor

(v) Temporary/Removable Penetration Seal
* used to maintain compartmentation but can easily be removed to install move services

eg at the compartment wall beneath a raise floor in an office building where data cables are frequently added/changed.

Question 5

Explain the difference between Thermoplastic and Thermosetting materials

Answer 5

Thermoplastic Materials
* do not soften when exposed to heat, if overheated they will typically burn or char.

• Used wher resistance to heat is important, ege kettles, plugs, laptops etc.

Thermosetting Materials (aka thermosoftening)
* plastics which soften when heated and can be reshaped, eg Nylon, Acrylic, Polystyrene.

Question 6

In relation to fire glazing explain the difference between Integrity Rated Galzing and Insulation Rated Glazing.

Answer 6

Integrity rated glazing

• will with stand exposure to fire whilst preventing the spread of flames, smoke and hot gases for the define period.
• can withstand thermal shock form Ffing medium.
• It will not, however, prevent the transference of heat from the fire to the unexposed side of the glass.

Signfied byt the Letter E

Insulation rated glass

• will withstand exposure to fire, prevent the spread of fie, smoke and hot gases whilst also prevent the transference of heat from the fire to the unexposed side of the galss for the defined period of time, after which the temperture of the uneffected side of the glass will begin to rise, albeit slower than with non-insulated glass.
• will also withstand thermal shock from Ffing medium.

Signified byt he letters EI