Fire stopping and penetration seals, cavity barriers, ductwork and dampers and the building envelope

Question 1

Describe open cavity barriers and state two locations where they would be used. (4 marks)

Answer 1

Description
Open cavity barriers such as those used in rain screen cladding systems are cavity barriers which are
open to allow ventilation and drainage in the cold state, but which either close in a fire, or are
inherently fire resisting providing fire separation in the cavity.
They are usually made from stone wool slabs faced with aluminium foil together with a reactive
component such as an intumescent which causes the seal to close in fire.
Areas of Use
Open cavity barriers are used in ventilated rain screen cladding, roof ventilation, eaves, within internal
walls in buildings and other areas where ventilation is required in the cold state. As with ordinary
sealed cavity barriers, they are not normally intended to act as fire separating elements which have
higher requirements for fire resistance. Although this should be checked at site.
Particular care is required in the installation of some open cavity barriers as these are normally difficult
to access after installation.

Question 2

Describe the factors to be taken into account when selecting and installing penetration seals
(4 marks)

Answer 2

a) Is the fire-stopping to be used in a wall or a floor, or a junction between fire-separating
elements?
b) If it is a floor, is it required to be loadbearing?
c) What fire resistance period is required?
d) How big is the gap or the opening?
e) Does the fire-stopping have to cater for movement in the fire separating element?
f) What kind and type of services, if any, are penetrating the construction at the opening?
g) How many services are there?
h) What size is each service?
i) How close are the services positioned to each other?
j) How close are the services positioned to the edge of the opening?
k) Is the fire-stopping system suitable for use with the intended elements of construction?
l) Is installation accessible for the particular type of service and firestopping being considered?
m) Is the seal required to have acoustic, air tightness or water resistance properties?
n) Is it required to have a particular reaction to fire performance?
o) Is it required to have particular electrical resistance characteristics?

Question 3

Describe the composition and use of sealants/mastics. (5 marks)

Answer 3

Sealants are generally manufactured from acrylic or silicone

They may be used to seal around any penetrating services where testing indicates their suitability. They are
also suitable when used in conjunction with coated batts/boards in all forms of fire resistant construction,
where openings are small, where penetrations are complex and where there is imperfection of fit between
building elements.

Question 4

Stone wool mineral products are supplied in a number of forms when used as firestopping.
State the forms that such products take and state the factors to take into account when
installing these products. (3 marks)

Answer 4

Mineral wool products are supplied in ablative coated batts and boards, mineral wool curtains, with a reinforcing mesh and preshaped strips. Less dense mineral wool products supplied in large slabs can be used as backing in a linear joint seal or smaller blank penetration seals and around cables.
Factors to take into account are fire rating required, support requirements of the system used and maximum aperture/cavity size. Ensure that different manufacturers products are not mixed and correct sealant is used as tested detail states i.e. 20mm annular 25mm depth. Substrate type and orientation (wall or floor or junction), substrate framing, service type, service size, service spacing, movement.

Question 5

Explain the purpose and operation of an intumescent damper. (5 marks)

Answer 5

The purpose of an intumescent damper is to maintain compartmentation, for a given period of time, where ductwork penetrates compartmentation.

To intumesce means to swell. The materials in an intumescent damper are activated in the heat of a fire, typically 120C to 270C. The pressure exerted by the swelling closes the airway, as the duct material softens due to heat, preventing the passage of fire beyond the compartment. Smoke can still pass an intumescent damper if the activation temperature has not been reached.

Question 6

In relation to the construction and design of the building envelope, describe how the use of
cladding can affect fire resistance. (3 marks)

Answer 6

Cladding can affect fire resistance by

Adding to the fire load
Poor design and fitting can create gaps that allow a route for fire spread

Question 7

Describe the purpose and the operational features of fire resisting rolling shutters. (6 marks)

Answer 7

The purpose of a fire resisting roller shutter is to provide compartmentation. Insulation properties are rquired if the shutter is more than 25% of the compartment wall in which it is located.

Operation

• A local heat detection release mechanism such as a fusible link, where for example, a fire
  shutter has been formed across a means of escape route
• An automatic release mechanism operated from remote smoke detection equipment or an
  alarm system
• A door closure delay device where an audio/visual warning may be deemed necessary in
  addition to the normal operational safety

Question 8

Describe the checks that you would carry out when inspecting the installation of ironmongery
fixed to fire doors. (6 marks)

Answer 8

Locks and lever handles

• Lock levers fully return to the horizontal after use
• Latch bolt is engaged smoothly and completely into the keep
• Wipe any metal dust deposits off the latch bolt and keep
• Adjust, lubricate or replace as per manufacturers recommendation

Hinges

• No visible wear, dark marks or stains around the hinge knuckle which could indicate wear and
  impending failure and 3 of them

Closing and opening devices
* Open the door fully and check it closes without binding on the floor
* Open the door to approximately five degrees and check again that it closes fully, engaging any
latch or seal

• Check the door closing speed to be approximately ten seconds from ninety degrees and
  ensure that the door does not slam
• Ensure that doors are not being wedged open
• Make sure that door hold-open devices are not straining the doors against the self-closing
  devices
• Check that mechanical hold-open devices have not been fitted
• Hold-open devices on fire doors should be electro-magnetic and connected directly to the fire
  detection and alarm system, so that they can be released automatically if there is a fire

Letterboxes are fire/arson resistant