Thursday, April 28, 2022

Safety Message: Fires in tunnels and underground stations

FTUGs can result in catastrophic loss of life although this is not the case for the vast majority of fires due to the effectiveness of fire safety controls.

RTOs should continue to identify new potential safety controls and make an assessment as to whether they are reasonably practical to implement as well as reviewing their current operations to ensure that existing fire safety controls are in place and effective.

Given fire safety is a specialist discipline, RTOs may be required to engage recognised fire safety specialists to accurately determine risk levels and determine which controls are appropriate for specific rail networks and operations. This may also be required to determine appropriate methods for demonstrating compliance to fire safety standards. Fire safety specialists should also be engaged to assess the impact of any proposed modification to rail infrastructure that may have an impact on fire safety.

ONRSR’s review into FTUGs identified causes and contributing factors across the four areas listed below. While not exhaustive and given the range of operational environments within the Australian rail industry, the following causes, contributing factors and controls should be noted.

CAUSES AND CONTRIBUTING FACTORS

The causes of FTUGs can be classified into organisational, technological or equipment factors, and individual factors.

1. Organisational factors e.g.

• Inadequate strategic planning and integration between the tunnel systems and railway operations e.g. no consideration of potential fire loads on rolling stock, evacuation times, and emergency services access as part of determining the overall fire safety risk for any given tunnel or underground station.
• Unclear division of responsibilities causing gaps in the management of fire risks, e.g. one or more stakeholders not discharging their duties regarding fire safety, as different parties have different responsibilities.
• Railway safety management systems not robust enough to account for reasonably foreseeable risks.
• Not making the necessary long-term investments in safety.
• Inadequate maintenance including tunnel maintenance.

2. Technological or equipment factors e.g.

• Faults on rolling stock or other station equipment such as escalators.
• Collisions and tunnel collapse.
• Electrical and other traction power system faults.

3. Individual factors e.g.

• Arson, explosion, or terrorist activities.
• Misadventure or recklessness such as smoking or discarding a cigarette-end or match on trains or at stations.

CONTROLS

While not exhaustive and given the range of operational environments within the Australian rail industry, the following controls should be noted. RTOs must consider a range of factors, including the likelihood of the hazard and the degree of harm to determine what controls are reasonably practicable to implement (see the ONRSR Guideline – Meaning of duty to ensure safety so far as is reasonably practicable SFAIRP for more information).

Elimination:

There is no single control that can be implemented that can eliminate fires in tunnels and underground stations. While not eliminating the risk, implementing the following controls can however reduce the risk.

Substitution:

Removing fire loads or controlling the amount of combustible material permitted in a tunnel or underground station reduces the risk of fires propagating. This includes:

• materials or goods carried by trains;
• material that form part of the train itself; and
• materials brought into the station e.g. vending machines, television screens.

Engineering:

RTOs have employed a variety of engineering controls which can be categorised into the following five (5) groups.

1. Compartmentation controls are designed to inhibit the spread of smoke, fire, heat as well as ensuring structural integrity within an underground station. Dividing the station area into a series of ‘fire tight boxes’, termed compartments, limits the spread of fire, helps people evacuate and allows emergency services to undertake rescue operations. Examples of compartmentation controls include but are not limited to:

• Fire doors: such doors minimise the risk of smoke and/or fires spreading through the station. They can be either self-closing (as soon as you open it, it closes because of the door closing mechanism attached) or automatic (closes automatically on detection of a fire using an electro-magnet). While these types of doors can still be opened, they close once a person has passed through.
• Fireproof walls: walls that are made of materials that are fire resistant. This can:
  • prevent cracking and failure of the wall due to the fire (also called spalling);
  • prevent the spread of the fire; and
  • ensure that, together with the fire doors, provide an effective barrier to inhibit fire spread.
• Junctions and joints: as well as doors and walls, junctions and joints designed to control the spread of smoke and fire will help mitigate the consequences. Controls can include the use of fire rated sealants and strengthening of the tunnel lining.
• Sealing around service penetrations: the running of electrical and plumbing services requires holes to be made through walls, these penetrations need to be sealed to inhibit the spread of fire, smoke and other noxious gases produced as a result of a fire.

2. Fire suppression system controls apply chemicals or fluids on fires to limit their spread. Examples include but are not limited to the following:

• Portable fire extinguishers can be used to extinguish small fires but often require training to ensure their use is effective.
• Gaseous suppression systems are used for rooms that may be higher risk due to the contents or to avoid damage to the equipment inside, e.g. computer server rooms, electrical substations and communication rooms. Gases are more effective in starving a fire of oxygen and less damaging to the contents inside a room than water. When fire or smoke is detected, gaseous suppression systems automatically activate and release or discharge an inert gas into the room.
• Sprinklers, also referred to as fixed firefighting systems, are activated by heat resulting from fires, and can be used to limit the spread of a fire or contain a fire that has started.
• Fire hydrants and fire hose reels enable firefighters to effectively extinguish fires allowing fire and allow emergency services to attack and extinguish smaller fires.

3. Ventilation controls control air flow underground stations and tunnels. They provide clean air for egress paths and routes, cross passages, safe places, including pressurisation; removing exhaust smoke and hot gasses safely away from people; and prevent/control the spread of smoke. Examples include:

• Forced ventilation systems are required as part of tunnels and underground stations to provide fresh air to people under normal operating conditions. However, the ventilation system should be designed to reduce the supply of fresh air to areas where fires are detected to reduce the spread of fire. Such systems also need to supply or maintain fresh to escape routes.
• Dampers in ventilation duct work in a similar manner to fire doors and can be used to prevent the spread of smoke and direct fresh air into escape routes.

4. Fire detection systems enable detection of fire during its early stages before it begins to spread. Examples include:

• Detection systems in a tunnel can trigger an alarm which can be relayed to network control to organise prompt emergency response, including preventing trains entering the tunnel, evacuation of trains already in the tunnel and firefighting.
• Automatic fire detection systems can also be used to trigger automatic fixed fire suppression systems as well as identify the location of the fire.

5. Escape and Refuge controls provide a safe place for people to escape and exit, or seek refuge, until it is safe for them to escape. Examples include:

• Fire escape stairs offer the simplest escape method however they may not be practical for deep or underwater tunnels.
• Fire refuges and cross passages are often used when the distance required to reach a point of safety is greater than what a person can reasonably walk. These form a safe refuge until emergency services can rescue the passengers.
• Running capability provides rolling stock the capability to continue running in the event of fire so that passengers can alight at a safe location.

Administrative:

Operators have employed a variety of administrative controls to minimise the risk of fire in tunnels and underground stations which can be categorised into two (2) groups.

1. Public communication system controls are controls which alert people to the risk of fire and direct them to a place of safety. Examples include:

• passive signs such as those showing exits and escape routes
• active signs and audio messages providing real time information to passengers, such as those that can be presented on passenger information displays or screens at stations.
• rolling stock passenger information displays, and auditory warnings / announcements provide information to passengers.

2. Emergency services and management systems controls include:

• Specialised equipment such as recovery trollies used in tunnels where conventional emergency vehicles cannot access, can be used to transport passengers or emergency services to or away from the fire.
• Fire indicator panels which is the controlling component of a fire alarm systems receives information about where fire detectors and alarms have been activated.
• Zone and emergency block plans which show where the fire detection and alarm zones, fire suppression systems, and main electrical switchboards are located.
• Emergency response which is initiated to evacuate and fight the fire once a fire has started and has been detected in a tunnel or underground station. This includes the plans and procedures of how the emergency response will be activated. The following includes, but is not limited to, the requirements response plans and procedures can consider:
  • the scope i.e. what scenarios it covers;
  • a list of emergency incidents and simulations to be prepared for, including tunnel-specific incident scenarios adapted for the local tunnel conditions;
  • a list of participating agencies;
  • training requirements; and
  • the need to be consistent with the self-rescue, evacuation, firefighting, and rescue facilities available.

• Centralised control systems which provide overall monitoring of the station, including any trains entering tunnels and underground stations, so that the emergency response can be centrally managed.

Many of the above controls are required as part of codes and standards which include, but are not limited to the

• National Construction Code and Building Code;
• AS4825 Tunnel Fire Safety;
• AS1851 Routine Service of Fire Protection Systems and Equipment; and
• International standards such as NFPA 130:2020 Standard for Fixed Guideway Transit and Passenger Rail Systems.,

This information is provided as guidance only and may not be applicable to all rail transport operators.