Most gas incidents in mining are preventable. The hazard is rarely a surprise to the engineers who know the mine, but the atmosphere changes shift by shift, and people cannot see, smell or feel most of the gases that harm them.
This guide explains the gases that matter on Ghanaian mine sites, summarises what the Minerals and Mining (Health, Safety and Technical) Regulations, 2012 (L.I. 2182) say about atmosphere monitoring, and sets out how to build a gas detection programme that works in practice.
The gases that matter on a mine site
Which gases you monitor depends on the orebody, the mining method and the equipment you run. The common ones are:
- Oxygen (O2): both deficiency and enrichment are dangerous. Low oxygen can occur in poorly ventilated workings, sumps and confined spaces.
- Methane (CH4) and other combustible gases: explosive in air at the right concentration, and the main hazard in gassy and coal mines.
- Carbon monoxide (CO): toxic, produced by blasting, diesel engines, fires and spontaneous heating.
- Hydrogen sulphide (H2S): toxic at low concentrations. At high concentrations it dulls the sense of smell, so people cannot rely on noticing it.
- Carbon dioxide (CO2): an asphyxiant that accumulates in low-lying and poorly ventilated areas.
- Nitrogen oxides (NO, NO2) and sulphur dioxide (SO2): present in blasting fumes and diesel exhaust.
- Hydrogen cyanide (HCN): a hazard in gold processing where cyanide is used.
What L.I. 2182 says about atmosphere monitoring
The regulations set out duties for mine managers on ventilation and atmosphere quality. The provisions most relevant to gas detection include:
- Regulation 179: adequate ventilation where people travel or work underground, with oxygen not less than 19% by volume and limits for carbon dioxide, carbon monoxide, sulphur dioxide, nitrogen dioxide, nitrous fumes and methane.
- Regulation 179(4): continuous monitoring of air quality so that carbon monoxide can be detected in main return airways, with data transmitted to a central control room at the surface.
- Regulation 186(1): a competent person determines the quantity, quality and speed of air, air temperature and dust at intervals not exceeding three months.
- Regulation 188: sampling of air where diesel equipment operates, including carbon monoxide and nitrogen oxides in the undiluted exhaust, at least monthly and after repairs.
- Regulations 223 and 239: in processing plants, mobile gas detection capable of measuring hydrogen cyanide, and fixed continuous detection with data logging and an audible alarm where hydrogen cyanide is likely to exceed 10 ppm.
This is a plain-language summary for general information, not legal advice. Regulation numbers refer to L.I. 2182. Always check the current regulation text and Minerals Commission guidance for your operation.
Personal, area and fixed monitoring: use all three
Each type of instrument answers a different question, and most sites need a combination.
- Personal monitors travel with the worker and measure the air at the breathing zone. They are the last line of defence and should be worn by everyone entering a hazardous area.
- Area monitors protect a location such as a confined-space entry, a work-zone perimeter or a plant area. Cloud-connected area monitors can relay alarms to a supervisor.
- Fixed monitoring points give continuous readings at defined locations, such as return airways, and feed a control room. This is how continuous carbon monoxide monitoring is normally delivered.
Bump testing and calibration: what each one is for
A bump test briefly exposes the instrument to gas to confirm that each sensor responds and that the alarms work. A calibration adjusts the instrument so that its readings are accurate against a known gas concentration. They do different jobs, and one does not replace the other.
- Bump test before each day's use. This is the common recommendation from manufacturers and industry guidance.
- Calibrate at the interval given in the manufacturer's instructions and your site's gas monitoring procedure, and after a failed bump test.
- Keep records for every test and calibration so you can show inspectors that instruments were verified.
What connected gas monitoring adds
Connecting instruments to software changes gas detection from a set of isolated devices into a managed programme. Industrial Scientific's iNet platform, for example, provides fleet management for calibration and bump-test compliance, live monitoring with alerts, and peer-to-peer alarm sharing between nearby instruments. The practical benefits are fewer missed tests, faster response to an alarm and an audit trail that is built automatically.
A checklist for building your gas detection programme
- Identify the gases and the locations where each could occur, for underground workings, surface pits and processing plants.
- Choose the instruments: personal monitors for every worker in the area, area monitors for fixed locations and fixed points for continuous monitoring.
- Set alarm levels in line with the regulations and your site's gas management plan.
- Establish bump-test and calibration routines, and decide where they are carried out.
- Train workers to wear, check and respond to their monitors, and rehearse alarm responses.
- Review alarm history regularly to find recurring problem areas before they become incidents.
Frequently asked questions
What are the main gases to monitor in a Ghanaian gold mine?
Oxygen, carbon monoxide, hydrogen sulphide and combustible gases underground, plus carbon dioxide and nitrogen oxides from blasting and diesel equipment, and hydrogen cyanide in processing plants. A site assessment confirms the right set for your operation.
Does Ghana require continuous gas monitoring underground?
L.I. 2182 regulation 179(4) requires continuous monitoring of air quality so that carbon monoxide can be detected in main return airways, with data sent to a surface control room. Check the current regulation text for the full requirements.
How often should a gas detector be bump tested?
Most manufacturers and industry guidance recommend a bump test before each day's use. Follow the manufacturer's instructions and your site procedure.