MineARC Tech Topic:
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Oxygen Systems
What are the oxygen systems supplied to a refuge chamber to keep occupants alive in the event of an emergency?
This MineARC Tech Topic explains the importance of multiple oxygen systems to a refuge chamber.
DID YOU KNOW?! Oxygen is the most important gas for
sustaining life. Our bodies are dependent on oxygen for
survival; it is consumed by our bodies in order to produce
energy.
Given that a refuge chamber is a sealed environment, it is vitally
important to consider how oxygen levels inside a refuge chamber
are managed. Oxygen levels of the “dead air space” will quickly be
consumed and with no breathing supply occupants would quickly
suffocate within a matter of a few hours. Monitoring and controlling
the internal atmosphere as well as air treatment and multiple
breathable air sources are therefore vital to refuge chamber
occupants over the duration of entrapment.
OXYGEN LEVELS
Amongst other things, ‘breathable air’ or air supplied to a refuge
chamber, should contain no less than 19.5% and no greater than
22% by volume of oxygen (AS/NZS 1715:2009).
For more information on Air Quality Standards, please view the
MineARC Tech Topic: Breathable Air article.
The normal lower working limit for oxygen levels is 19%. At 18% a
slight increase in breathing effort will occur. At 16% a flame lamp
will go out, but still only a slight increase in breathing and heart
rates would be noticeable and some cognitive impairment may
occur. At 14%, impaired judgement and coordination are noticeable.
However, as levels fall below 12%, cardiac damage and vomiting
can occur. At 10% and below, a lapse into unconsciousness and
death will occur.
On the contrary, oxygen levels higher than 23% presents a
fire hazard. Though not itself flammable, oxygen promotes
and accelerates combustion, so an oxygen rich environment
increases the combustibility of materials and is undesirable in any
environment, particularly a confined space. Handling oxygen supply
equipment therefore requires care in ensuring that no grease or oil
come into contact with the oxygen gas flow path.
DID YOU KNOW? To maintain a level of oxygen that is both
safe to breathe and non-hazardous, it is necessary to
replace the oxygen as it is being consumed.
SOURCES OF OXYGEN
The two standard sources of breathable air within a MineARC refuge
chamber are incoming, filtered and regulated compressed air from
an external source and oxygen cylinders. A recommended optional
third source is an oxygen candle.
OXYGEN SUPPLY 1: COMPRESSED AIR
Compressed air is simply the atmospheric “air” from above ground
being pushed through pipe lines down to the refuge chamber via
a compressor. Before compressed air can be considered suitable
for breathing, it needs to be filtered from airborne water particles,
oil contaminants and pollutants such as carbon monoxide and
hydrocarbons from diesel exhausts.
The order of a filtration system’s elements is critical in ensuring the
compressed air supplied to a refuge chamber is safe for occupants
to breathe. The MineARC Compressed Air Management System
(CAMS) features a four-stage filtration process. CAMS is tested to
ISO 12500-1, and has been specifically designed to meet AS/NZS
1716:2003.
The flow rate of the compressed air in to the chamber is adjusted
with a regulator and the compressed air required to sustain a
breathable atmosphere within a chamber is calculated at 85L/m
(3CFM) for the chamber and 85L/m (3CFM) per person thereafter.
CAMS Manifold
Air
Toxicity
Monitor
Flood Protection
•
•
•
•
Four-Stage Air Filtering:
Water Separation
5 Micron Pre-filter
0.01 Micron Coalescing Filter
0.01 Micron Absorbent Filter
Auto Drain
www.minearc.com
COMPRESSED AIR
MANAGEMENT SYSTEM
(CAMS)
MineARC Tech Topic:
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Oxygen Systems
OXYGEN SUPPLY 2: OXYGEN CYLINDERS
In the event that the compressed air source fails, the refuge
chamber must have an independent source of oxygen. MineARC
utilise compressed oxygen from cylinders.
Oxygen cylinders reintroduce oxygen in to the refuge chamber at
the rate it is being consumed. Compressed oxygen from a cylinder
is released into the chamber through a regulator that controls the
flow rate. Flow is set at the rate of occupant consumption.
Oxygen consumption rates vary from person to person and
with activity. MineARC use 0.5 Litres per person per minute in
calculations involving the consumption rate of oxygen in refuge
chambers. This allows a safety margin and for variations in
individual size and requirements of chamber occupants.
Using this rate of consumption, it is possible to work out oxygen
requirements and how many oxygen cylinders are necessary to
meet the total amount of oxygen required for an occupied refuge
chamber. This is calculated as follows:
number of chamber occupants
x rate of consumption
x minutes in an hour
x number of hours duration.
The flow rate can be calculated as
follows:
number of occupants x flow rate.
MineARC recommends the use of
the largest medical grade oxygen
cylinder - ‘G size’ - which contains
8200L of breathable oxygen.
In conjunction with oxygen cylinders, air scrubbing is utilised to
chemically remove contaminants or undesired gases like carbon
dioxide (CO2) and carbon monoxide (CO) produced in normal human
metabolic processes, and filter the internal atmosphere.
For more information on MineARC’s Scrubbing Systems, please view
the MineARC Tech Topic: Scrubbing Systems article.
MINEARC’S AUTOMATED OXYGEN DELIVERY SYSTEM
An option for MineARC Refuge Chambers is the Automated Oxygen
Delivery System (AODS) which takes the guess work out of correctly
maintaining oxygen levels in the refuge chamber. Once the system is
activated, the AODS continuously measures the internal oxygen level
and will disperse metered amounts of oxygen from a compressed
oxygen cylinder, to maintain oxygen levels between 18.5% and 23%
inside the refuge chamber. The system’s flow rate is limited to 15
Litres per minute, which is suitable for up to 30 persons.
This is advantageous for a number of reasons:
• Ensures chamber will not
become oxygen rich
• Ensures oxygen levels do
not drop too low
• Minimises wastage of
oxygen in cylinders by only
dispensing what is being
consumed
• Reduces handling of oxygen
supply equipment
AUTOMATED OXYGEN
• Reduces chance for human
DELIVERY SYSTEM
error in equipment operation
OPTIONAL OXYGEN SUPPLY 3: OXYGEN CANDLE
Using an exothermic chemical reaction to
generate oxygen, the oxygen candle is the third
and final method of breathable air supply. This
Consideration also needs to be
would be used in an extreme emergency, in
given to whether the regulator used
the event of failure of the first two systems,
can handle the required flow rate.
to either extend the duration or to buffer a
response time to exit the chamber. The candle
OXYGEN
will burn for approximately 60-90 minutes,
CANDLE
producing 2600L of oxygen. This can provide
approximately 20 hours of breathable air for
4 people. An oxygen candle cannot have its
oxygen production regulated or halted and
once ignited, it will produce oxygen at a rate OXYGEN IGNITER
of approximately 28 Litres per minute until it is
OXYGEN CYLINDERS
REGULATOR
MATCH
exhausted.
For further information regarding MineARC’s Oxygen Systems and recommendations, please visit www.minearc.com or email
[email protected] to speak to a MineARC representative.
www.minearc.com