Coal MiningHard Rock MiningPetrochemicalTunnelling

What is the Ideal Safe Refuge Chamber Duration?

Determining the ideal refuge chamber duration in stand-alone mode is an often contested discussion. It poses more questions than answers without concise agreement by governments and industry bodies worldwide.

Safe haven or refuge chamber duration should be determined on a risk-based approach. Every mine, construction site, plant, or facility is different and should be assessed based on its unique conditions, and the overall emergency response plan.

refuge-chamber-duration
Refuge Chamber in an underground mine

A chamber’s ‘stand-alone’ duration needs to consider the resources available; at the very least it must factor in escape routes, equipment, as well as the skills and capabilities of Emergency Response Teams (ERT).

Stand-alone mode occurs when the refuge chamber is cut from external air and power sources, resulting in the use of a finite source of battery backup and breathable air. A refuge chamber, while connected to mains power and mine air can continue to sustain life indefinitely. However, in these instances, the supply of food and water becomes more pressing.

Survivability in a refuge chamber focuses on characteristics of meeting fundamental requirements to sustain life, including maintaining a respirable atmosphere, and habitable environment, as well as the provision of basic needs such as water.

Mining, resources and construction industries are high-risk businesses. There is a careful balance between emergency preparedness and the protection of personnel, against the costs of over insurance. Each emergency is a unique event, and it is impossible to predict with exactness, the period required to sustain miners before rescue.

Safe Haven and Refuge Chamber Duration for Industries

Refuge Chamber Duration for Metalliferous and Non-Metal Mines can range from 24 -96 hours.

Common hazards which can cause the use of a refuge chamber include fires, rock fall, hazardous gases and smoke.

Many countries have adopted the 2013 Western Australian DMP Guidelines for Refuge Chambers in Underground Mines as the global benchmark for safety standards in underground mining. These guidelines set the minimum stand-alone refuge chamber duration of 36 hours, based on a worst-case scenario.  Necessarily conservative, the period is based on the immediate and ongoing danger of a tyre fire, with additional time for mine rescue teams to act and reach a chamber.

Experiences worldwide, from incidents where reliable information is available, suggest most chambers are used for a duration between two and ten hours. However, the set of conditions associated with each of these events is so varied that no clear pattern can be identified to establish an acceptable duration. While longer incidents and extreme cases are less common, they are still prevalent, as recent history has shown with the Copiapó mining accident in 2010 and Beaconsfield, Tasmania in 2006.

Refuge Chamber Duration for Coal Mines can range from 48 – 96 hours.

Common hazards which can cause the use of a refuge chamber within the coal industry include fires, explosions, rock fall, hazardous gases and inundation.

Coal mines have significant quantities of fuel that can burn for days, so it is suggested the rescue and evacuation strategies should be different to hard rock mining. To provide for an added margin of safety, Mine Safety and Health Administration (MSHA) has determined that it is necessary to require refuge chambers in the United States coal industry to be able to sustain life for a minimum of 96 hours.

refuge-chamber-duration
Inside an underground refuge chamber

A stand-alone duration of 96 hours aims to assist any rescue effort by providing the necessary time for the ERT to reach trapped miners safely. There are a number of variables which can significantly affect rescue activities, including the depth of the mine, the geology of the overburden, and the above-ground terrain. Coal mine rescue protocol requires monitoring of the mine atmospheres and assessing the risk before mine rescue teams enter and make progressive steps towards trapped miners.

Successful mine rescue progression often requires the repair of damaged infrastructure, e.g., roof control systems, and ventilation controls.

To arrive at the 96-hour requirement in this final rule, MSHA reviewed recent and historical data on entrapments. While most safety and health professionals and researchers agree that refuge alternatives can sustain trapped persons, there is not general agreement on the amount of time that the refuge alternative should be capable of supporting miners.

Refuge Chamber Duration for Tunnel Projects can range from 24 – 72 hours.

Common hazards which can cause the use of a refuge chamber within the tunnelling and underground construction industry include fires, explosions and hazardous gases.

The common use of a refuge chamber in tunnelling and underground construction is a reasonably recent safety initiative. On an international scale, the International Tunnelling and Underground Space Association (ITA) are the peak industry body representing health and safety standards for the industry.

As part of the guidelines laid out by the ITA, the need for refuge chambers should be evaluated as part of the tunnelling project’s risk assessment. Although, they do state that every active face of a tunnel project should have a refuge chamber.

Similar to the mining industries, the duration of a tunnelling refuge chamber is assessed based on the time required to conduct a rescue. A minimum of 24 hours is recommended by the agency, with the ability to provide additional resources to extend this period if the risk assessment requires.

In some regions of the Americas, tunnelling and mining regulations overlap. Tunnel Refuge Chambers are required to comply with the same safety standards stated in mining regulations, including Chile (48 hours) and Peru (72 hours).

Safe Haven and Shelter-in-Place Duration for the Petrochemical Industry can range from 4 – 12 hours.

Common hazards which can cause the use of an above-ground or shelter-in-place within the petrochemical, refining and power generation industries include fires, explosions and hazardous gases.

There is currently no minimum standard for the petrochemical industry.

In the United States, many companies utilise the American Petroleum Institute (API) Recommended Practice 753. These guidelines outline requirements for process plant portable buildings to reduce risk to personnel from explosions, fire and toxic release. Considerations include shelter-in-place design, placement, and the overall emergency response plan for portable buildings located in areas where a toxic release can reach ERPG-3 levels.

Additional principles referenced are the Emergency Response Planning Guidelines (ERPGs) developed by the American Industrial Hygiene Association (AIHA). The ERPG Handbook is developed to be used as a tool to assess and design adequate emergency response plans in the event of a chemical release. The values focus on a release period of 60-minutes, at varied chemical toxicity levels. However, a minimum of two to four hours is commonly requested by industry personnel.

ERPGs are air concentration guidelines for single exposures to agents and are intended for use as tools to assess the adequacy of accident prevention and emergency response plans, including transportation emergency planning, community emergency response plans and incident prevention and mitigation.

Unfortunately, ERPG-1 is the most commonly used guide – yet is not a safe standard for the industry. ERPG-1 suggests a low hazard level; individuals exposed to the maximum airborne concentration of a chemical release, over the hour period, would experience only mild, short-term health effects.

It is advised ERPG-3 be utilised as a minimum standard for emergency shelters until an industry standard is established. Due to the nature of the industry, toxic concentration and exposure present a much higher risk. For higher risk environments, the exposure to toxicity levels for an individual less than, or equal to, one hour are equal to the ERPG-3 concentration. Subsequently, as the exposure produces the same toxicity dose, the health effects would also be the same.

Current Refuge Chamber Legislation

Mining

Western Australia: 36 Hours

Department of Mines and Petroleum, 2013, Refuge Chambers In Underground Mines – Guideline

Duration of independent services and power

A refuge chamber should be capable of 36 hours of self-sustained operation to allow sufficient time for a rescue to be completed.

Refuge chambers are expected to support a full complement of occupants while operating in stand-alone mode under the worst-case scenario. Such a situation is provided by a large rubber-tyred vehicle catching fire when travelling in the main intake airway. The danger of re-ignition, a tyre explosion or both may persist for up to 24 hours, and it is deemed unsafe to approach the vehicle during this period.

Although it may be feasible for mine rescue teams to work their way past the burned-out unit and bring the occupants of the refuge chamber or chambers out on foot, it should not be assumed that this would be possible in all cases. One or more of the occupants may be unable to walk, and vehicular access may be essential. An additional 12 hours is a reasonable safety margin to allow for the clearance of any obstruction and restoration of normal services.”


Chile: 48 Hours

Ministerio de Mineria, 2004, Decreto Supremo No.132

Decreto 34, MINERÍA Art. ÚNICO, D.O. 14.06.2013

Artículo 610

En la situación señalada en el artículo precedente, el Servicio podrá exigir también la construcción de refugios de acuerdo con el avance y características de la faena, pudiendo ser estocadas de seguridad, contenedores o construcciones similares.

Estos refugios deberán contar con los elementos indispensables que garanticen la sobrevivencia de las personas afectadas por algún siniestro, por un período mínimo de 48 horas, tales como alimentos no perecibles, agua potable fresca, sistema de comunicación con la superficie o áreas contiguas, elementos de primeros auxilios y manuales explicativos para auxiliar a lesionados.”

Decree 34, MINING Art. UNIQUE, D.O. 06/14/2013

Article 610

“In the situation indicated in the preceding article, the Service may also require the construction of shelters in accordance with the progress and characteristics of the task, and may be safety lunches, containers or similar constructions.

These shelters must have the essential elements that guarantee the survival of people affected by a disaster, for a minimum period of 48 hours, such as non-perishable food, fresh drinking water, communication system with the surface or contiguous areas, elements of first aid and explanatory manuals to help injured people.”


Ontario, Canada: Minimum 8-hour duration and up to 24 hours depending on the mine design

Mines & Aggregates Safety & Health Association, 1998, Guidelines For Mine Rescue Refuge Stations

“Duration of Occupancy

This may be the controlling factor in the design of many refuge stations. A minimum 8 hour occupancy time is suggested. In other cases, this may be longer, up to 24 hours, depending on the location; for example, in the case of single access to a refuge station.

The maximum occupancy time is considered to be that time from the start of occupancy until an upper limit of 3% carbon dioxide and a lower limit of 16.25% oxygen is reached.”


Turkey: 36 Hours

Ministry of Labor and Social Security, 2017, Refuge Chambers Installed In Underground Mine Workplaces

“Sığınma odasının teknik özellikleri

MADDE 6

… (3) Sığınma odalarının kullanılması durumunda içinde bulunan kişilere en az 36 saat yetebilecek solunabilir hava sağlanır. Maden basınçlı havasının kesilmesi durumunda içeride güvenilir oksijen kaynakları bulundurulur. Sığınma odasına oksijen sağlanırken, kişilerin sağlık ve güvenliğini tehdit etmeyecek şekilde karbondioksit ve karbonmonoksitin de seyreltilmesi veya filtrelenmesi sağlanır.

(4) Odalarda; klima, hava temizleme, nem alma, aydınlatma, uyarı ışıkları, haberleşme, gaz izleme sistemleri ve sığınma odasındaki diğer elektrikli ekipmanlar için en az 36 saate kadar yedek enerji kaynağı bulundurulur.”

“Technical specifications of refuge chambers;

ITEM 6

… (3) In case of using the refuge chambers in emergency situation, chamber should provide breathable air to refuges minimum 36 hours. In case of mine pressured air failure, there must be reliable oxygen sources inside the chamber. While providing oxygen to refuges, both CO2 and CO gasses must be filtered-scrubbed by the system without causing any danger to human health.

(4) Air conditioning, air scrubbing, moisture removing, lighting, warning lights, communication and gas monitoring systems must be powered minimum 36 hours with back-up power source .”

Coal Mining

United States: 96 hours

Mine Safety and Health Administration, 2008, 30 CFR Parts 7 and 75 Refuge Alternatives for Underground Coal Mines; Final Rule

“MSHA developed this final rule based on Agency data and experience, NIOSH recommendations, research on available and developing technology, state regulations, and comments and testimony from the mining community.

The final rule includes requirements for—

  • Testing and approval of refuge alternatives and components of refuge alternatives;
  • Assuring that refuge alternatives are readily available, capable of sustaining trapped miners for 96 hours, and maintained in operating condition; and
  • Training miners to locate, deploy and use, maintain, and transport refuge alternatives.”

Peru: 72 Hours

Ministry of Energy and Mines, 2010, Decreto Supremo que aprueba el Reglamento de Seguridad y Salud Ocupacional y otras medidas complementarias en minería

“Artículo 138º.

En toda mina subterránea se construirá estaciones de refugio para que, en caso de siniestro, el personal tenga dónde aislarse y quede provisto de aire, agua potable -en una cantidad mínima de consumo para setenta y dos (72) horas- y un sistema de comunicación adecuado para facilitar su salvataje. El personal será instruido sobre la ubicación de dichas estaciones.”

“Article 138º.

In every underground mine, refuge stations will be built so that, in the event of a disaster, the personnel will have to isolate themselves and be provided with air, potable water -in a minimum amount of consumption for seventy-two (72) hours- and a system of adequate communication to facilitate your rescue. The personnel will be instructed on the location of said stations.”


Mexico: 96 Hours

NORMA Official Mexicana, 2012, NORMA Official Mexicana NOM-023-STPS-2012, Underground Mines and Opencast Mines – Conditions of Security and Health at Work

“8.14.5 Los refugios deberán estar provistos de los elementos indispensables a que se refiere el numeral 8.14.6, de tal manera que garanticen la sobrevivencia de los trabajadores en su interior, por un periodo de al menos 96 horas.”

“8.14.5 The shelters must be provided with the essential elements referred to in the numeral 8.14.6, in such a way as to guarantee the survival of the workers inside it, for a period of minus 96 hours”

Tunnelling

International: 24 hours

International Tunnelling and Underground Space Association – Working Group N°5 Health and Safety in Works, 2014, Guidelines for the Provision of Refuge Chambers In Tunnels Under Construction

“1.8 Duration of use

The period of time for which the chamber could be in use should be assessed on the likely time required to affect a rescue. It is recommended that refuge chambers are designed for a minimum occupancy time of 24 hours. Where this is considered insufficient, the project risk assessment should include a determination of the minimum occupancy time.”

Petrochemical

There is currently no minimum standard for the petrochemical industry.

American Industrial Hygiene Association (AIHA), 2018, Emergency Response Planning Guidelines (ERPGs)

“…Emergency Response Planning Guidelines (ERPGs®) are values developed by the AIHA® Guideline Foundation’s Emergency Response Planning (ERP) Committee to assist emergency response personnel in planning for accidental or intentional catastrophic chemical releases to the community. ERPGs® are developed to meet the need for community emergency exposure planning guidelines, particularly for chemicals that have high potential for uncontrolled releases and those that might pose particular hazards because of their volatility and toxicity.…

ERPG–1: The maximum airborne concentration below which nearly all individuals could be exposed for up to 1 hour without experiencing more than mild, transient adverse health effects or without perceiving a clearly defined objectionable odor.

ERPG–2: The maximum airborne concentration below which nearly all individuals could be exposed for up to 1 hour without experiencing or developing irreversible or other serious health effects or symptoms that could impair an individual’s ability to take protective action.

ERPG–3: The maximum airborne concentration below which nearly all individuals could be exposed for up to 1 hour without experiencing or developing life-threatening health effects.”

American Petroleum Institute (API), 2007, Recommended Practice 753: Management of Hazards Associated With Location of Process Plant Portable Buildings

In addition to explosion and fire hazard guidance, considerations for toxic release hazards should be taken. Portable buildings located in areas where a toxic release can reach ERPG-3 levels should meet either of the following:

  • Be designed for shelter-in-place, or have an emergency response plan that includes the following:
    • Evacuation plan that directs personnel to a designated “shelter-in-place” or specified assembly area
    • Plan to account for occupants
    • Personal protection equipment (PPE) to be used by all occupants during the evacuation if required.
  • Portable buildings used for Shelter-In-Place should have the following features at a minimum:
    • Heating, ventilation and air conditioning systems (HVAC) capable of rapid shutdown of the system or placement in recirculation mode, whichever is more appropriate. This HVAC shutdown response should be included in the emergency response plan;
    • Exhaust fans and duct penetrations of exterior surfaces equipped with a positive seal against infiltration of outside air;
    • Emergency communications equipment;
    • PPE to be used by all occupants during the evacuation as necessary;
    • Seals for windows and doors that are present.

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