Specification 31 Fire and smoke control systems in buildings containing atriums

This Specification sets out the requirements for the design and operation of systems of fire and smoke control in buildings containing an atrium.

A sprinkler system (other than a FPAA101D or FPAA101H system) complying with Specification 17 must be installed in every building containing an atrium, except where varied or superseded by this Specification.

(1) A roof of an atrium which does not have the FRL prescribed in Specification 5 or the Deemed-to-Satisfy Provisions of Part C3 must be protected by automatic sprinklers arranged to wet both the covering membrane and supporting structure if the roof is—

1. less than 12 m above the floor of the atrium or the floor of the highest storey where the bounding construction is set back more than 3.5 m from the atrium well if a Class 2, 3, 5 or 9 part of a building is open to the atrium; or
2. less than 20 m above the floor of the atrium or the floor of the highest storey where the bounding construction is set back more than 3.5 m from the atrium well if a Class 6, 7 or 8 part of a building is open to the atrium.

(2) The temperature rating of sprinkler heads required by (1) must be within the range 79°C – 100°C

The floor of the atrium must be protected by sprinklers with—

1. the use of sidewall pattern sprinkler heads together with overhead sprinklers where dictated by the dimensions of the atrium; and
2. sprinkler heads of the quick response type.

(1) Where an atrium is separated from the remainder of the building by walls or doors incorporating glazing, a wall wetting system must be provided to protect the glazing as follows:

1. On the atrium side of the glazing — to all glazed walls which are set back more than 3.5 m from the atrium well.
2. On the atrium side of the glazing — to all glazed walls which are not set back, or are set back 3.5 m or less, from the atrium well, for all levels which are less than—
   1. 12 m above the floor of an atrium or the floor of the highest storey where the bounding wall is set back more than 3.5 m from the atrium well if a Class 2, 3, 5 or 9 part of the building is open to the atrium; or
   2. 20 m above the floor of an atrium or the floor of the highest storey where the bounding wall is set back more than 3.5 m from the atrium well if a Class 6, 7 or 8 part of the building is open to the atrium.
3. On the side of the glazing away from the atrium well — to all glazing forming part of the bounding wall at each storey.

(2) Sprinklers must be located in positions allowing full wetting of the glazing surfaces without wetting adjacent sprinkler heads.

(3) Sprinkler heads must be of the quick response type and have a maximum temperature rating of 74°C.

(4) The rate of water discharge to protect glazing must be not less than—

1. on the atrium side of the glazing—
   1. 0.25 L/s.m² where glazing is not set back from the atrium well; or
   2. 0.167 L/s.m² where glazing is set back from the atrium well; and
2. on the side away from the atrium well — 0.167 L/s.m².

(5) In addition to that of the basic sprinkler protection for the building, the water supply to required wall wetting systems must be of adequate capacity to accommodate the following on the atrium side of the glazing:

1. Where the bounding walls are set back less than 3.5 m from the atrium well — wall wetting of a part not less than 6 m long for a height of not less than—
   1. 12 m above the floor of an atrium or the floor of the highest storey where the bounding wall is set back more than 3.5 m from the atrium well if a Class 2, 3, 5 or 9 part of the building is open to the atrium; or
   2. 20 m above the floor of an atrium or the floor of the highest storey where the bounding wall is set back more than 3.5 m from the atrium well if a Class 6, 7 or 8 part of the building is open to the atrium.
2. Where the walls are set back 3.5 m or more from the atrium well — wetting of a part not less than 12 m long on one storey.

(1) Basic sprinkler and wall wetting systems protecting a building containing an atrium must be provided with easily accessible and identified stop valves.

(2) Sprinkler and wall wetting systems must be provided with independent stop valves.

(3) Sprinkler heads protecting the roof of the atrium must be provided with a stop valve.

(4) Stop valves to wall wetting and roof sprinklers may be of the gate type.

(5) All sprinkler and wall wetting stop valves must be monitored to detect unauthorised closure.

Except where varied or superseded by this Specification, mechanical air-handling systems in a building containing an atrium must comply with AS 1668.1.

Mechanical air-handling systems serving an atrium must be designed to operate so that during a fire—

1. a tenable atmosphere is maintained in all paths of travel along balconies to required exits during the period of evacuation; and
2. smoke exhaust fans serving the atrium are only activated when smoke enters the atrium; and
3. central plant systems do not use the atrium as a return air path; and
4. central plant systems which use return air paths remote from the atrium—
   1. cycle to the full outside air mode; and
   2. stop supply air to the fire affected storey or fire compartment; and
   3. continue to fully exhaust the fire affected storey or fire compartment and reduce the exhaust from other storeys or fire compartments by at least 75%; and
   4. continue to supply air to fire compartments or storeys other than the fire affected storey or fire compartment; and
5. fans performing relief or exhaust duty from the atrium stop normal operation; and
6. floor by floor, or unitary, air-handling plant serving a single fire compartment or storey—
   1. ceases normal operation in the fire affected storey or fire compartment; and
   2. commences full relief or exhaust from that fire affected storey or fire compartment; and
   3. continue to supply air to fire compartments or storeys other than the fire affected storey or fire compartment.

(1) The smoke control system must be activated by—

1. operation of an automatic fire alarm; or
2. operation of the sprinkler system; or
3. a manual start switch.

(2) All controls for the smoke control system must be located—

1. in the fire control room; or
2. in the emergency control centre (if any); or
3. adjacent to the sprinkler control valves; or
4. incorporated in the Fire Indicator Panel.

A smoke exhaust system serving an atrium must be designed on the basis of—

1. the sprinkler system limiting the size of a fire to—
   1. a heat output of 1.5 MW and perimeter of 7.5 m if a Class 2, 3, 5 or 9 part of the building is open to the atrium; or
   2. a heat output of 5 MW and perimeter of 12 m if a Class 6, 7 or 8 part of the building is open to the atrium; and
2. a smoke plume reaching a level 3 m above the highest storey having a path of travel to a required exit along a balcony bounding the atrium well, and not less than—
   1. 12 m above the floor of an atrium or the floor of the highest storey where the bounding wall is set back more than 3.5 m from the atrium well if a Class 2, 3, 5 or 9 part of the building is open to the atrium; or
   2. 20 m above the floor of an atrium or the floor of the highest storey where the bounding construction is set back more than 3.5 m from the atrium well if a Class 6, 7 or 8 part of the building is open to the atrium; and
3. the smoke exhaust system discharging smoke at a rate of not less than that shown in Figure S31C10 for the appropriate height of smoke plume and fire size—
   1. from the top of the atrium; or
   2. horizontally, where calculations of wind velocity induced pressure profiles for the building verify that the exhaust system will operate effectively for all wind directions.

Notwithstanding S31C10(c), the average upward air velocity in the atrium, due to the required smoke exhaust quantity must—

1. be not less than 0.2 m/s at any level over an 18 m height above the floor of the atrium; and
2. not exceed the following maximum velocities in atriums of constant cross sectional plan area:
   1. For occupancy classification qualifying for 1.5 MW fire size — 3.5 m/s.
   2. For occupancy classifications qualifying for 5 MW fire size — 5 m/s.

(1) Smoke exhaust must be provided by fans capable of continuous and required operation for a period of not less than 1 hour when handling exhaust gases at 200°C.

(2) Where a Class 2, 3 or 9 part of a building adjoins an atrium, the atrium must be provided with a minimum of 3 fans each capable of 50% of the total required smoke exhaust capacity.

(3) Atriums other than those referred to in (2) must be provided with a minimum of 2 fans each capable of 50% of the total required smoke exhaust capacity.

Notwithstanding S31C12, automatic vents complying with AS 2665 may be used, except where a Class 6 part of a building adjoins the atrium, in lieu of exhaust fans provided that—

1. the height from the atrium floor to the bottom of the highest vent is not more than 12 m; and
2. the vents are fitted with a remote manual operation switch located adjacent to the sprinkler control valves or incorporated in the Fire Indicator Panel.

(1) Uniformly distributed make-up air must be provided to the atrium exhaust system from—

1. outside the atrium at or near the lowest storey level; and
2. relief air from non-fire storeys.

(2) A discharge volume sufficient to maintain a velocity of not less than 0.1 m/s towards the atrium well must be provided on all storeys where the bounding wall is set back from the atrium well.

(3) The requirements of (1)(a) are satisfied if make-up air is provided to the atrium exhaust system in such a manner as to prevent, as far as possible, disturbance of the smoke layer due to turbulence created by the incoming air, through—

1. openings directly from the outside air to the atrium and located as close as practicable to the lowest level of the atrium; or
2. ducts from the outside air to the atrium which deliver air as close as practicable to the lowest level of the atrium and, where passing through any other fire compartment having an FRL of at least 60/60/60; or
3. a combination of (a) or (b).

Except where superseded by this Specification, automatic fire detection and alarm systems in a building containing an atrium must comply with AS 1670.1.

Smoke detection within an atrium—

1. must be provided within all outside air intakes and at individual floor return air intakes of all air-handling systems to initiate automatic fire mode operation, and where applicable, comply with the restart facilities in AS 1668.1; and
2. must operate at an obscuration level not greater than 0.5% per metre with compensation for external airborne contamination as necessary; and
3. must sample air within the atrium and in storeys where the bounding wall is set back more than 3.5 m from the atrium well; and
4. must be calibrated to compensate for smoke dilution where sampling occurs within return air path common to more than one room; and
5. may incorporate beam type detectors to sense smoke in an atrium in a Class 5, 6, 7 or 8 building with an effective height of not more than 25 m if the beam detectors are—
   1. located at intervals of not more than 3 storeys; and
   2. arranged to scan at 90 degrees orientation to adjacent beam units.

Smoke detection systems must be located at all return and relief air openings associated with the building air-handling systems and be—

1. of the sampling type system as required in S31C16; or
2. of the point type photoelectric smoke detector.

(1) A break-glass fire alarm point must be provided at each door to a fire-isolated stairway, fire-isolated ramp or fire-isolated passageway.

(2) A staged alarm must be provided where an air sampling type smoke detection system is provided for the atrium, and must operate as follows:

1. Alert building management when abnormal smoke levels of 0.03% obscuration per metre are detected.
2. Initiate a second alarm to management and start all smoke control systems including pressurisation of escape routes when smoke levels of 0.07% obscuration per metre are detected.
3. Automatically call the fire brigade, activate the emergency warning and intercom system, and de-activate all plant not necessary for fire safety within the building when smoke levels of 0.09% obscuration per metre are detected.

(3) Beam and point type smoke detectors required must simultaneously operate all functions referred to above and activate at the level set out in AS 1670.1.

A building containing an atrium must be provided with an emergency warning and intercom system which—

1. complies with AS 1670.4; and
2. incorporates visual warning devices that—
   1. operate upon the evacuation signal; and
   2. display the word “EVACUATE” in red with letters conforming with the requirements of the Deemed-to-Satisfy Provisions of Part E4 for exit signs.

(1) If a required path of travel to an exit is within an atrium, a suitable alternative power supply must be provided to operate required safety systems, including sprinkler systems and fire hydrant pumps, air handling systems, alarms, warning and communication systems and emergency lighting circuits.

(2) The alternative power supply must—

1. be connected automatically if the normal power supply fails; and
2. if located within the building, be separated from the remainder of the building by an enclosure with an FRL of at least 120/120/120; and
3. be connected to the safety systems by means of cabling complying with C3D14(3).

(3) The requirements of (1) are satisfied by—

1. a single medium voltage supply taken from an electricity substation situated within, or adjacent to, the building concerned where the power supply to the substation consists of two or more high voltage cables each taking electricity from separate transformers; or
2. two or more medium voltage supplies each taking electricity from separate electricity substations situated—
   1. outside the building concerned; and
   2. at a suitable distance from each other; or
3. a single medium voltage supply taken from an electricity substation together with an electricity generating plant capable of—
   1. generating a medium voltage supply; and
   2. starting and taking the required electrical load within a period of not more than 30 seconds from the time of normal supply failure.

Required fire-isolated exits in a building containing an atrium must be protected from the entry of smoke in accordance with E2D3.