NCC Tutor lesson - Understanding fire safety in the NCC

Slide 1:

Welcome to Understanding fire safety in the NCC

Slide 2:

The focus of this presentation is on the fundamentals of fire safety in buildings, including fire safety terminology and the aims of the fire safety provisions in the NCC.

Slide 3:

This is what you will learn about in this presentation. What causes fire, approach to fire safety in the NCC, key fire safety concepts & terminology, active and passive fire safety measures, other useful resources.

Slide 4:

What causes fire and how do we suppress it? The fire triangle diagram presents a key concept that underpins fire suppression methodologies. The removal or depletion of one of the 3 fire criteria stops the fire from continuing to burn. A fire will “burn out” when starved of oxygen, fuel or heat, for example when it has used up all the available oxygen or fuel, or when it is cooled to the point that the chemical reaction can no longer take place. The provisions within the NCC make use of this understanding of what causes fire, and what can suppress it.

Slide 5: 

Fire safety in the NCC. The NCC fire safety requirements predominantly focus on the safe evacuation of occupants before exposure to untenable conditions, and preventing damage to other buildings, i.e. minimising the spread of fire from one building to another. 

‘Untenable conditions’ are conditions in which human life is not sustainable due to prolonged exposure to smoke, heat or toxic gas.

Stopping the combustion process can contribute to fire safety in buildings, however it is not a critical requirement of the NCC. 

The NCC also doesn’t facilitate comprehensive property protection. The NCC fire safety provisions do not require that the building is prevented from burning down, only that the occupants can evacuate safely and the fire doesn’t spread to neighbouring buildings.

Regulations addressing fire safety in buildings have been in place for nearly 2000 years. They have evolved over time as a result of learning from experience, learning from research, political expediency.

Current fire safety regulations can include measures that were used almost 2000 years ago. The first major historical fires that lead to regulations being introduced were the Great Fire of Rome in 64AD. Rome burnt for 4 days. Once the fire was extinguished, the then Emperor Nero implemented a new urban development plan designed to stop the spread of fire. This included wider open roads, restrictions on the height of houses, more space between houses, requirements to build houses in brick or stone, no common walls allowed. 

The Great Fire of London in 1666. Embers from a bakery chimney ignited a thatched roof on an adjacent building. London burnt for 4 days with 80% of buildings destroyed. Subsequently, fire control measures were introduced, including hand-held water suppression (buckets/hand pumps), fire breaks – created by pulling down buildings with hooks and ropes or controlled gunpowder explosions, requirements to build houses of brick or stone, wider streets, introduction of building surveyors to enforce these new regulations.

Many of these same measures are essential parts of current fire safety regulations around the world. Even now, the development of regulations of the built environment to minimise the impact fire is an evolving process. 

Slide 6:

Key concept: Fire-resistance level (FRL). The fire-resistance level of a building element is a measure of how long the element can control or reduce the spread of fire/gases/heat and retain its own structural strength when exposed to fire. 

FRL is a graded performance over time of a building element exposed to a test fire. It is measured in minutes and basically states how long a material or form of construction will last when subject to a fire in a building. The Australian Standard AS 1530.4 is generally used to define a material’s FRL.

An FRL has 3 parts, each of which measures one aspect of the fire-resistance of an element. Structural adequacy, which measures its ability to maintain stability and loadbearing capacity when exposed to fire. Integrity, which measures how long it can resist the passage of flames and hot gases. Insulation, which measures how long the material can maintain a required minimum temperature on a surface not exposed to fire. That is, how long before other surfaces become too hot as a result of fire on another surface of the material.

If one aspect is not applicable, the FRL will include a dash (--) for that aspect.

For example 90/60/30 means that the material (or form of construction) will be structurally adequate (i.e. hold the load that it is carrying) for 90 minutes. It will maintain its integrity (i.e. will hold its shape or form) for 60 minutes and will insulate against heat from one side to the other for 30 minutes.

FRLs are specified for many materials/elements/assemblies in many different parts of the NCC. For example, in Volume One, they are specified in Sections C, D, E, G and I (as well as in the State/Territory Appendices in the Schedules).

Specification 1 of the various NCC Volumes contains the procedures for determining the FRL of different building elements.

The next slide is an activity with 3 questions to apply this concept of fire-resistance levels.

Slide 7:

Interpreting fire-resistance levels

Question 1:  What level of structural adequacy must each opening have? Possible Answer 1:

None of the listed types of openings in a fire wall must have any level of structural adequacy. That is, none of them need to comply with AS 1530.4 to maintain their stability and load bearing capacity in a fire.

Question 2: How long must each type of opening maintain a temperature on unexposed surfaces? Possible Answer 2: Self-closing or automatic closing doors in fire walls must maintain a temperature on unexposed surfaces for at least 30 minutes.

Windows (of any kind) and other openings in fire walls have no requirement to maintain a temperature on unexposed surfaces for any time.  (Other requirements may apply.)

This is the insulation portion of the FRL i.e. the third value.

Question 3: 3. How long must each type of opening resist the passage of flames and hot gases? Possible Answer 3: All the listed kinds of openings in a fire wall must resist the passage of flames and hot gases for at least 60 minutes.

This is the integrity portion of the FRL, i.e. the second value.

Slide 8:

Key concept: Fire-source feature. A fire-source feature for a building is a point from which a fire could spread to the building, OR to which a fire could spread from the building. 

This includes the far boundary of a road, river or lake which adjoins the allotment (e.g. an allotment boundary that is on the other side of a street). It can also be the side or rear allotment boundary (even if no building or structure is on the adjoining allotment). 

A fire source feature can also be an external wall of another building on the same allotment (besides a shed, garage, carport, etc.).

The definition of external wall is slightly different for Volume One and Volume Two. Note that, as the illustration shows, Class 10 buildings/structures on a block are treated separately and are not included in the definition of a fire-source feature. Fire-source features need to be identified so that appropriate fire safety measures can be taken to prevent the spread of fire.

Slide 9: 

Example: FRLs and fire-source features. 

Question 1: What minimum FRL is required for an external wall in a Class 5, Type A construction building, if the wall is 2 m from a fire-source feature? Answer 1: FRL = 120/90/90.

Question 2:  What minimum FRL is required for an external wall in a Class 7b, Type A construction building, if the wall is 1 m from a fire-source feature? Answer 2: FRL = 240/240/240

Question 3: What is the relationship between the minimum insulation requirement of an external wall and the distance between the wall and the fire-source feature? Answer 3: As the distance increases, the minimum requirement for insulation in an external wall of a Type A construction building decreases. The requirement for integrity reduces similarly, but only once the distance reaches more than 3 m. Minimum requirements for structural adequacy remain the same for a wall exposed to a fire-source feature, regardless of how far away that feature is. This holds true for any Class 2-9 buildings.

This means that an external, load-bearing wall in a Type A building must be able to maintain its structural stability and load-bearing capacity when exposed to fire or the same minimum time regardless of the closeness of a fire-source feature. 

Slide 10:

Key concept: Combustible and non-combustible

Non-combustible is defined in 2 parts. (a) For a material; and (b)For construction or part of a building.

For a material, this means a material which is or is not deemed to be combustible as determined by the Australian Standard AS 1530.1 Combustibility Tests for Materials.

As you can tell from the examples given, non-combustible materials will not propagate fire spread during a building fire.

Obviously, for fire safety a non-combustible material is better. However, not every material or building element is equally exposed to fire, so they do not all need to provide the same level of protection. Also, sometimes, more combustible materials have properties that make them desirable in other ways. So, sometimes there is a need or desire to balance or trade-off the combustibility of a material with its other performance characteristics. 

Non-combustible materials may be required in isolation or as an addition to a requirement for an element to have a FRL. 

The fact that a material is classed as non-combustible, does not imply that the material has an FRL. 

If the provisions require use of a non-combustible material with a certain FRL, you must use a material that clearly meets both of these criteria.

There is a concession for certain types of combustible materials, which is discussed shortly.

Slide 11:

Key concept: Combustible and non-combustible

Like non-combustible materials, combustible materials are also defined in 2 parts. (a) For a material; and (b) For construction or part of a building.

Combustible materials is also a defined term from Schedule 1 Definitions in the NCC. 

Essentially, if a material can’t withstand the AS 1530.1 test, it is combustible. 

Although a building built entirely from non-combustible materials would have fire-safety advantages, it would be difficult to achieve and therefore impractical, which is one reason why the BCA reserves non-combustibility requirements for key high-risk areas of certain buildings, such as the external cladding of high-rise buildings. Nevertheless, the BCA achieves fire-safety by other means, including fire-resistance (as already covered) and fire hazard properties (which will be covered shortly).

There is a concession for certain types of combustible materials, which is discussed on the next slide.

Slide 12:

Concession: materials that may be used for elements required to be non-combustible

May be used wherever Volume Two requires a  non-combustible material

A similar list appears in Volume One, Clause C2D10(6).

Slide 13:

Key concept: Fire-hazard properties

Fire hazard properties capture the specific properties of a material (or assembly of materials) and how it performs when exposed to fire.

Fire hazard properties provide ratings for how quickly a material (or assembly of materials) will catch fire, quickly the fire will spread once alight, and much smoke is produced once that material is on fire.

Fire hazard properties are a means of controlling the performance of exposed elements during early stages of fire. They are typically used to measure the performance of linings (i.e. floor coverings or wall linings) to determine if they are appropriate for use in buildings. 

There are different types of fire hazard properties defined in the NCC including the average specific extinction rate, critical radiant flux, flammability Index, smoke-Developed Index, smoke development rate, spread-of-Flame index, group number, smoke growth rate index.

Each of these properties is either a Defined term in the NCC, or it references another section of the NCC. It is important to understand the meaning of each property, how it is derived and what it can be used for.

Slide 14:

Complete the sentences below

Option 1:  A material is WHAT if it does not readily ignite or burn. The answer is non-combustible.

Option 2:  Building elements that could be exposed to fire are required to meet a minimum WHAT. The answer is fire-resistance level (FRL).

Option 3:  A WHAT for a building is any feature from which fire could spread to the building, or to which fire could spread from the building. The answer is fire source feature

Option 4: A building material’s WHAT indicate how that material will behave under specific fire test conditions. The answer is fire hazard properties.

Slide 15:

How do we achieve fire safety?

To achieve fire safety in buildings, the NCC prescribes minimum fire safety requirements.

This is made up of individual elements that in combination form a fire safety system within the building.

A fire safety system may have one or more different elements, each of which could be targeted to one of the 4 aims listed on the slide.

Active fire safety measures are those triggered when exposed to the products of fire such as heat, smoke or toxic gas; OR which are manually operated. 

Passive fire safety measures are those that do not respond or activate when subjected to fire or fire products. They are measures that are generally built into the building fabric and are focused on fire resistance.

Slide 16:

What are active fire safety measures?

Active fire safety measures are those triggered when exposed to the products of fire such as heat, smoke or toxic gas, such as an automatic smoke alarm. Which are manually or automatically operated. For example, a fire extinguisher on a wall which must be manually operated. A smoke alarm triggers when it senses the presence of smoke. 

Examples of active fire safety measures include hose reels, fire extinguishers, fire blankets, smoke alarms, sprinklers, break-glass alarms, emergency lighting, fire fighters/emergency services.

Remember, active fire safety involves exposure to a fire product – like heat or smoke which may precede the start of a flame. 

Slide 17:

What are passive fire safety measures? 

Passive fire safety measures are those that do not respond or activate when subjected to fire or fire products.

These measures are focused on fire resistance – they are all about resisting ignition in the first instance, and preventing the spread of flame if a fire does occur.

They include fire rated walls, roofs, floors, doors, stairways, compartmentation (i.e. dividing large spaces into separate fire compartments), use of non-combustible cladding, providing open space between buildings and potential fire sources. 

They are generally part of the building fabric and are required to have one or more of the following attributes fire-resisting materials, resistance to the incipient spread of fire, non-combustibility, fire hazard properties, smoke-proof, solid core.

Slide 18:

Achieving fire safety in Volumes One and Two. Fire safety measures in Volume One and Volume Two are designed to allow for safe evacuation and to limit the spread of fire.

However, because the type of buildings and their use across both Volumes are different, there are some differences in the fire safety provisions. There is no one size fits all approach with any aspect of building design and the same is true for fire safety design.

Volume One covers a broad range of building classifications and uses, so there are different risks associated with fire.

Some building classifications are associated with inherently risky activities, from the point of view of fire, such as manufacturing or laboratory work. Warehouse buildings and other commercial buildings can also store flammable items, or items that give off toxic smoke. There is an increased risk of fire in these types of buildings, and an increased risk to health and amenity for the occupants/users of the buildings. The fire safety measures required in these classes of buildings reflect that increased risk.

Class 2-9 buildings can also often be large buildings and multi-storey buildings, which increases the time it takes to evacuate the building in the case of a fire. Fire safety measures need to take account of the need for occupants to have a longer timeframe to evacuate safely than might be required in a smaller building. 

Similarly, in some of these classes of buildings the occupants may be incapacitated, for example in a hospital or residential care home.  When occupants need assistance to evacuate, then evacuation will take longer, so this needs to be considered in the design and construction of fire safety measures. 

Additionally, in Class 3 apartment buildings, Class 2 buildings or Class 4 parts of a building, occupants may be asleep at the time the fire occurs, so they need to be alerted to the fire, and given the time to evacuate safely.

Key responses to these fire associated risks in Class 2-9 buildings include those listed on the slide.

Volume Two covers a smaller range of building classifications (predominantly housing) with different risks, but there are fire risks nevertheless.

Some of the activities that typically take place in Class 1 and Class 10 buildings can cause a fire, for example, cooking which is a common cause of house fires. Other common causes of house fires are outdoor barbeques or other outdoor fires, overloading of electrical systems (too many plugs into one outlet), smoking, particularly in bed.

Occupants of Class 1 buildings may also be asleep at the time the fire occurs, so they need to be alerted to the fire, and given the time to evacuate safely.

Evacuation can generally quicker, however, because Class 1 buildings tend to be smaller (than a commercial building) and only one or 2 storeys high. So, not as much time is needed to evacuate the building.

Key responses to these fire associated risks in Class 1 and 10 buildings include those listed on the slide.

Slide 19:

Other useful resources

There are some ABCB Standards related to fire safety, particularly for NCC Volume One. As with all other referenced documents, these are not mandatory, but may be used to comply depending on the pathway chosen. One example is the ABCB Fire Safety Verification Method Standard. 

The ABCB also provides a range of handbooks, that contain non-mandatory guidance information.

Similarly, there are case studies, videos and other resources available from the ABCB website that might be useful to them. These do not contain any mandatory requirements.

Slide 20:

What 3 inputs are needed to sustain a fire? Answers: 1. Oxygen, 2.Heat, 3.Fuel.

All 3 inputs are required to sustain a fire, so fire safety measures in the NCC are generally targeted towards reducing one or the other of these inputs.

Slide 21:

The fire safety provisions in the NCC are designed to save people from death or injury and save buildings from burning down in a fire. Warn building occupants, allow them to evacuate safely and stop a fire from spreading to other buildings or structures. Warn building occupants, allow them to evacuate safely and stop a fire from burning the building down.

Stop buildings from catching on fire and save people from death or injury. If you selected Option 2, yes that’s right. 

Slide 22:

Summary. Fire requires fuel, oxygen and heat. Removing one or more of these slows or stops the fire. Many fire safety measures are targeted at reducing one or more of these inputs

Overall aim is to protect lives, and prevent the spread of fire between buildings, not focussed on property protection. Buildings must be designed/built to allow for safe evacuation. Requires appropriate fire safety systems, using active and passive fire safety measures.

Slide 23:

Key points

Fire source features. Expose a building to the risk of fire from outside. Can result in fire passing from one building to another. 

Appropriate fire safety rated materials and elements must be used in relevant situations or locations. 

Different ways of specifying fire safety characteristics of materials/assemblies – FRL, 
non-combustible, fire hazard properties

Concession allows for use of some (combustible) materials wherever a non-combustible material is required.

Slide 24:

Thank you for your time. That brings our presentation on understanding fire safety in the NCC to a close. If you’d like more information please visit abcb.gov.au