Bad Air

Air quality is especially a concern in larger mines. Many dangerous gasses do not have a color or odor, but are nonetheless hazardous. In the old days miners would take canaries down into coal mines. The birds had small lungs and were especially sensitive to methane and carbon monoxide. If the canary stopped chirping and died miners would know that they needed to get out. Today we use more technically precise hand held instruments that can warn us of dangerous gas levels.

4 Gas or O2 Monitor

If you have a smaller budget, look for a good O2 monitor. These can be had for around $150.00. A 4 gas monitor is more expensive. Plan on about $1000.00 for a good one. These come in a wide variety and can be equipped to monitor from one to four different gasses. With a 4 gas monitor you can be more informed about the mine atmosphere. If you use an O2 only monitor, plan on moving as soon as that O2 level varies. For all underground mines the air quality must have a minimum oxygen content of 19.5% and a maximum CO2 content of 0.5%. Any variation in O2 could indicate an increase in other gases. If you don’t know, don’t risk it. Get out now and ventilate the mine later.

Areas of risk

Looking down a mine tunnel

Looking down a mine tunnel

1. Areas with no ventilation or no convection circulation (Convection circulation is the motion of warm air rising and then cooling off and sinking, producing a continuous circulation of air. Convection circulation is caused by the mine walls either heating or cooling incoming air)
2. Pools of stagnant water
3. Declines/ shafts (Air quality can change quickly with elevation)
4. Areas with heavy timbering (Decay of organic material can cause unhealthy gas levels)

Gasses can pool and stratify due to their specific gravity. Stratified gasses may be disturbed by merely walking through an area and cause symptoms when passing back through the area. Specific gravity is the ratio of the density of a substance to the density of a reference substance. Some gasses are “heavier” and sink while others are “lighter” and rise. In the case of mines, hazardous gas will stratify in a column based on its specific gravity. Gasses may pool, build-up, dissolve in water or stratify in areas of little or no air circulation such as:
1. Shaft bottoms
2. Dead-end drifts or stopes
3. Declines
4. Isolated areas
5. Pools of stagnant water

If you encounter standing water, carefully stir up the water in a small area and hold a gas meter close to the water. Sometimes the water will actually bubble up when disturbed, due to the saturation of dissolved gasses in the standing water. Assess standing water before passing by or through it.
The Mine Safety and Training Authority (MSTA) will be offering a course that will provide more details on what gases are hazardous and what to monitor underground, including the symptoms dangerous gases can cause.

The Mine Safety and Training Authority (MSTA) will be offering a course that will provide more details on what gases are hazardous and what to look out for, including the symptoms dangerous gases cause.

Mining Terminology – Dangerous gas levels

Black Damp – Nitrogen dioxide / Carbon dioxide
After Damp – Carbon dioxide / nitrogen dioxide and nitrogen monoxide
Fire Damp – any mixture of flammable gasses
Stink Damp – Hydrogen sulfide / Sulfur dioxide
White Damp – Carbon monoxide

The advice regarding safety, found above, does not cover every danger you might encounter in a mine and is not a substitute for sound judgement. We recommend becoming as educated as you can on mine safety. The more you know the better chance you will have of enjoying your mine and extracting the ores without incident.

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