Frequently Asked Questions

Do you need a mine refuge chamber?

You need to install a mine refuge chamber when:

• There is no escape-way or secondary means of exit from the mine
• Miners are working in remote areas of the mine, away from the normal access route into the mine
• Developing new levels
• Developing a new mine
• Re-entering an old mine

When initial mine development is underway, interim safety procedures are necessary until refuge chambers are established underground. The use of portable refuge chambers or the provision of oxygen self-rescuers are alternatives if a permanent refuge chamber is not practical.

How many chambers do you require?

The number of chambers and their size depend on the maximum number of workers expected to use the chamber at one time. Be prepared for contingencies, such as when additional individuals could be present at any location (e.g. geologists, visitors, inspectors, trainees, managers, etc.).

Contact RANA for help assessing your needs.

Where should refuge chambers be located?

Locate a refuge chamber at these points in your mine:

• Main or normal travel routes
• As close as possible to the greatest number of working places
• A safe distance from hazardous areas such as:
• Explosives magazines or storage containers (60 m or 200 ft)
• Electrical transformers greater than 5 KVA (15 m or 50 ft)
• Garages or fueling bays (in the event of a fire, the chamber must be located where there will be minimal effect)
• Blasting operations and concussion zones
• Where inadvertent entry of uncontrolled vehicles is possible
• Where there is ready access to mine rescue teams
• Where the ground is safe or well supported

How long should it take to evacuate to a refuge chamber?

The chamber should be within a maximum 15 to 30 minute walk for any crew member. If the length of time to get to a refuge chamber is greater than 30 minutes, then self-rescuers should be considered for those workers.

How many miners will need to evacuate to and occupy the refuge chamber?

This will depend on the number of miners and other workers within a 15-30 minute walk of the chamber. Be prepared for contingencies, such as when there could be additional individuals at any location (e.g. geologists, visitors, inspectors, trainees, managers, etc.)

What’s the maximum amount of time it could take for rescuers to reach the refuge chamber?

A mine’s rescue plan should include the maximum time it will take to rescue trapped miners.

Calculating the maximum time for rescue is the responsibility of the mine. These calculations are based on many factors (e.g. distance to rescue, type of accident, is there a mine rescue team on site or does the team have to come from another mine, etc.).

What are your sources of breathable air?

Breathable air considerations include more than just oxygen levels; too much carbon dioxide poses an equally deadly risk to trapped miners.

There are three main sources of breathable air in a refuge chamber:

1. Dead air space within the refuge chamber

To determine if there is enough dead air space to support your people you must consider:

• The size of the chamber
• The maximum number of occupants
• The maximum amount of time until rescue

However, be aware of other sources of air contamination within your mine that could compromise the air quality within your refuge chamber. Ensuring your refuge chamber is airtight will keep toxic gases out of the chamber.

2. The Mine's compressed air pipelines

A mine’s compressed air line could provide adequate breathable air to occupants of a refuge chamber if it provides greater than 100 cfm air flow. However, your mine safety plan must be prepared for damage, disruption or contamination of the line.

3. RANA’s Refuge One Air Centre

RANA’s Refuge One Air Centre provides breathable air for up to 36 hours, independent of mine power or compressed air line integrity.

Can compressed air cylinders, oxygen candles or high pressure oxygen cylinders be used as a source for breathable air?

No, these systems do not address the proper control of carbon dioxide, which can quickly build up and contaminate your occupants’ air supply.

What are safe levels of carbon dioxide and oxygen in a sealed refuge chamber?

In a sealed refuge chamber without ventilation, falling oxygen and rising carbon dioxide concentrations pose varying degrees of discomfort and potentially life threatening circumstances to the occupants. The size of the chamber and how long occupants will be contained will impact the air quality (see below for details). Safe values must be determined by your mine’s Industrial Hygienist.

What level of carbon dioxide is acceptable in a sealed refuge chamber?

• 350 ppm: Normal carbon dioxide concentrations
• 5000 ppm: The Time-Weighted Threshold Limit Value (TLV-TWA), where occupants would experience increased breathing rates
• 10,000 ppm: Headaches occur
• 30, 000 ppm: The Short-Term Exposure Limit (TLV-STEL); no more than 15 minutes at this level
• 50,000 ppm: Causes panting and discomfort; intoxication will occur within 30 minutes
• 100,000 ppm: Unconsciousness occurs
• over 100,000 ppm: Unconsciousness followed by death within one minute

What level of oxygen depletion is acceptable in a sealed refuge chamber?

• 20.9% Oxygen: The normal atmospheric oxygen concentration
• 19.5% Oxygen: The minimal acceptable level of oxygen
• 18% Oxygen: Occupants will require additional effort to breathe
• 16% Oxygen: Flames are extinguished and the occupants’ pulse and breathing rate will increase
• 14% Oxygen: Occupants experience fatigue upon exertion, emotional upset, impaired judgment, and faulty coordination
• 12% Oxygen: Occupants’ respiration is impaired, causing heart damage, poor judgment, discomfort, vomiting, and nausea
• Below 10% Oxygen: Unconsciousness and death occur

How long would it take for these levels to become dangerous?

Depending on the size of the chamber and the number of occupants, studies have shown likely levels of 5000 ppm carbon dioxide, the Time-Weighted Threshold Limit Value (TLV-TWA), will be reached in less than one hour and dangerous levels (20,000 ppm) are reached within four hours.

Furthermore, depletion to 18% oxygen, which causes increased breathing rate, could be reached in less than five hours and dangerous levels (less than 16% oxygen) in less than eight hours.

How do I determine occupancy times for a refuge chamber?

The maximum safe time within a refuge chamber depends on the size of the chamber, the number of occupants, the expected time of occupancy in a worst case scenario, the acceptable levels of CO2 and O2 and the source (if any) of breathable air.

RANA suggests designing and equipping your chamber to keep the occupants alive for at least 24 hours.

Download our Refuge Chamber Information Sheet to help you evaluate your refuge chamber and prepare your plan.

How do I determine the  air quality in a refuge chamber?

To calculate the air quality exposure limits expected from your refuge chamber, download our Quality of Air in Refuge Chambers. RANA’s Tommyknocker is also available with an optional gas monitor to test air quality.

Is the Refuge One CSA approved?

Our Refuge One Air Centre is manufactured to field-testing standards. There are currently no CSA standards for this type of unit, so the unit itself is not CSA approved. However, the 120 volt charger is CSA approved, as are all other components in the unit.

Learn more about the Refuge One's field testing results.

What kind of carbon dioxide absorbents can be used in the Refuge One?

RANA’s Refuge One Air Centre is designed to use a particular size of carbon dioxide absorbent to obtain maximum efficiency. Please contact us for more information about the type of carbon dioxide absorbent we recommend.

How long will the batteries and soda lime supply last before they need replacement?

5 years

How many occupants fit in The Tommyknocker?

The standard 14 ft (4267 mm) chamber accommodates 10 occupants; additional 2 ft (610 mm) sections can be added to increase the chamber's capacity.

What type of power does The Tommyknocker use?

The Tommyknocker (and the Refuge One Air Centre) require 120V AC and 60 Hz charger inputs and 12V DC outputs. We can also supply 220V and 50 Hz units (other voltages and frequencies are available).

Is the Refuge One Air Centre included in the price of The Tommyknocker?

The Tommyknocker can be quoted with or without the Refuge One.

What options are available for The Tommyknocker?

Contact RANA for more information and prices on these additional features available for The Tommyknocker:

• 24 litre chemical toilet
• Water dispenser
• First aid kit
• Compressed air system
• Carbon monoxide scrubber
• Portable gas monitor
• Air conditioner