What does ‘safe’ mean in materials developed for tunnels, trains and transport?

safety and non-combustibility tunnels trains and transport

Traditional insulation and non-combustibility are easily glossed-over topics. Ascertaining what constitutes passive fire protection, as opposed to risk reduction through provision of safe materials near passengers and operators, takes a reasonable sense of awareness and due diligence. Here is a guide to non-combustible acoustic treatments and insulation.

According to the Australian Building Codes Board, “The greater the risk of fire and the complexity (or duration) of evacuation, the greater the number of components that are required to be non-combustible”. (1)  

The purpose of including appropriately classed materials is to ensure due diligence and provide protection to firefighters in the execution of their duty, as well as safeguard occupants from illness or injury while evacuating a structure during a fire. 

The basic fundamental purpose of non-combustibility – including application appropriate materials – aims to keep a loss of life to a very low level and limit property damage.

Secondary to this is to protect other property from physical damage caused by the structural failure of any construction.

Many products claim to be non-combustible, but have they really been tested to a non-combustible standard? How prolific is the issue of non-conforming materials, and how can engineers truly trust they are working with tested and certified materials.

Where there is a non-combustibility requirement, it is there to control or limit fire load. It is important that the element should not burn – this is inherently tied to the material property. 

The factors that, measured together, deem a material does satisfy the requirement of non-combustibility are the occurrence of a flame from combustion, heat release, and mass loss from combustion. It is also prudent to measure other properties, such as smoke generation.

“Universal” is a term closely associated with definitive “way” or direction to achieve a certain goal. However, variations and testing compliance differences exist between methods and regions, so true non-combustibility can sometimes be misunderstood or even misrepresented.

Tunnels, trains and smoke toxicity

No matter where the authority or jurisdiction lies for tunnel construction and operations across a given infrastructure project, the materials used to build and line said areas must conform – preferably to an international standard,  

“From the point of view of fire initiation, growth and development in the context of protection of occupants,” (2) using safe materials to insulate is paramount, given the potential to burn or ignite. 

Tunnels in particular need to provide no-smoke emissions (or as low as possible) due to the time taken for egress and the toxicity level risk existing in the air even before a fire starts, given that they are areas that can have confined or limited airflow.

Traditional insulation systems can vary, however the latest technology moves towards fibre-free solutions for walls, floor and cavities and the realisation of how it makes sense to include more considered, more robust materials. 

In terms of acoustic control of reverberatory noise (as opposed to heat and thermal insulation), high performance is calibrated by its sound absorption, measured by either an NRC (noise reduction coefficient), SAA (sound absorption average) or sound absorption coefficient (αw). 

Yet when performance can be tuned to various frequencies and customised, it is still non-negotiable that the material must conform to non-combustibility status. 

The BCA defines non combustibility as “not deemed” combustible under AS1530.1Combustibility Test for Materials. The traditional sense of non-combustibility was simply to prevent the involvement of the combustible materials and fabric of a building or tunnel in a fire.

Addressing thermal transfer, insulation and innovative materials

The science doesn’t lie. The best way to ensure non-combustible construction is to choose long lasting materials with good fire properties. Where coatings are required to protect these materials, select, non-toxic low-VOC water-based compounds.

Specialised formulations are available to inhibit corrosion formation (Decicoat T35), or designed to intumesce when exposed to fire (Decicoat P60), protecting structural elements. 

Intumescent coatings prevent thermal transfer by effectively insulating the surface temperature of the component. It does this by extending its volume up to 100 times, creating a thermally insulating barrier.

When applied, it extends the time that the substrate maintains structural integrity, to “protect escape routes from collapse (beyond from smoke, from fire)” (1) during an evacuation.  

There are standard materials for construction – and then there are those with advanced, laboratory tested properties. 

Solutions from experienced teams

Reverberation inside rail line tunnels can potentially raise dB readings inside carriages to uncomfortable noise levels. 

Fitting tunnel interiors with highly absorbent panels, such as Pyrotek’s non-combustible Reapor and Viterolite, can provide impressive results to reduce reverberation within the tunnel space. It has also been shown to reduce the radiation of sound at tunnel openings, lessening community impact. (3)

Broad experience in structural fire protection in strict offshore environments, stringent international testing and certification are some of the qualities offered by experienced teams. Pyrotek are relied upon by infrastructure projects and building innovators globally. 

This partner content is brought to you by Pyrotek. For more information on Reapor and Viterolite, visit https://www.pyroteknc.com/.

1 https://abcb.gov.au/Resources/Publications/Research/FCRC-Evaluation-of-Non-Combustibility-Requirements

2 https://abcb.gov.au/Resources/Publications/Research/FCRC-Evaluation-of-Non-Combustibility-Requirements

3. http://www.datakustik.com/fileadmin/user_upload/PDF/Papers/Paper_SoundPredictionTunnelOpenings_Probst_0408.pdf

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