Large Isolated Building, Fire Loads and Fire Compartments

large-isolated-building

Large Isolated Building, Fire Loads and Fire Compartments

In general, pharmaceutical manufacturing facilities (usually of Class 7 and 8) tend to occupy large areas and volumes (large isolated buildings), due to the nature of the operations (such as tall process equipment availability, high capacity storage, etc.). In principle, larger spaces have higher potential fire loads.

Based on this assumption, and in order to limit the size of any possible fire in a building, the National Construction Code (NCC) imposed area and volume limitations to all Class 5-9 buildings. This space/size limitation is achieved with the application of compartmentation – meaning that large buildings are divided into fire compartments, essentially as a means to mitigate risk.

Maximum Size of Fire Compartments or Atria
Table 1: Maximum Size of Fire Compartments (or Atria)

The NCC sets out the maximum permissible sizes of fire compartments in the Table 1 above. As seen, the larger floor area allowance requires the more fire-resistant type of construction. So, in order to construct large facilities, it is required either to increase building’s ability to resist a fire or to divide building into smaller (fire) compartments. Buildings must be designed and constructed in a way to satisfy these limitations. In other words, the size of any fire compartment and similarly atrium, cannot exceed the figures specified in the table – except for ‘large isolated buildings’, which are granted some concessions from the floor area and volume limitations.

The Term ‘Large Isolated Building’

Under some conditions, the NCC allows the size of a fire compartment to exceed that specified in Table 1.

Size of a fire compartment may exceed:
1) up to 18000 m2 floor area and 108000 m3 volume, if;
a building of Class 7 or 8;

  • contains maximum 2 storeys and
  • has a minimum 18 m wide open space around, or

a building of Class 5-9 has;

  • a sprinkler system throughout (satisfying the requirements specified within the code) and
  • a perimeter vehicular access or

2) over 18000 m2 in floor area or 108000 m3 in volume, if;

a building of Class 5-9 has;

  • a sprinkler system throughout (satisfying the requirements specified within the code) and
  • a perimeter vehicular access.

If there exists more than one large building on the same allotment, it is required that either;

  • each building separately meets one of the listed options above, or
  • if they are located closer than 6 m to each other – regarded as one building, they collectively satisfy one of the listed options above.

The terms ‘open space’ and ‘vehicular access’ standing out within the definition of ‘large isolated building’, should be discussed in more detail. The NCC explains the requirements for both in a clear and detailed way, as they provide great benefit in firefighting.

Requirements for open space

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In order to minimise the risk of fire spreading to any building on an adjoining allotment, the NCC requires the provision of open space around large isolated buildings and clearly sets out the requirements to ensure that it functions effectively and does not end up impeding fire-fighting in time. According to the code, open space needs;

  • to be minimum 18 m wide around the building.
  • to be completely within the allotment.
    However, it can also include any road, river, or public place adjoining the allotment except the furthest 6 m of it – meaning that the part that falls beyond the line drawn 6 m from the furthest edge of that road, river, etc. is not included.
  • to include vehicular access (satisfying the requirements specified within the code).
  • not to be used for some other purposes such as storing or processing of materials.
  • to be kept clear of any building except for security guard houses and service structures (such as electricity substations and pump houses)

Requirements for vehicular access

For large isolated buildings, the NCC requires the provision of vehicular access so as not to impose restrictions on firefighting. This vehicular access also provides access to the building for other emergency services staff (such as ambulances). According to the code, vehicular access needs;

  • to provide an uninterrupted forward movement around the building and exiting to a public road.
  • to have a minimum net 6 m width – used only for vehicular and pedestrian access and kept clear of any other usage.
  • to be entirely located within 18 m from the building
  • to provide reasonable access for pedestrians to the building
  • to be constructed as hardstand – capable of withstanding heavy vehicles
  • to have an unobstructed height appropriate for the operation of fire brigade vehicles
  • to be completely within the allotment.
    (However, public road can be regarded as vehicular access if meets the other requirements.)

In order to meet all these requirements, it is advisable to liaise with the local fire brigade with respect to the perceived firefighting capability.

In net effect, these listed requirements for open space and vehicular access look something like this:

Minimum Requirements for Open Space and Vehicular Access
Figure 1: Minimum Requirements for Open Space and Vehicular Access

Please contact PharmOut if you require any assistance.