Environmental Monitoring

Ensuring the areas that we work in are safe is one of the paramount considerations when risk assessing when entering a confined space or a process operation.

Mines and tunnels will operate a forced ventilation network comprising of fans and ducting. The fresh air will be forced to working areas within a mine or tunnel, such as the production face, or the TBM (Tunnel Boring Machine).

Monitoring of toxic and flammable gases in a tunnel construction project is mandated in the UK under BS6164, and the majority of tunnel construction projects will install fixed environmental monitoring stations at intervals of between 300m and 500m.

MTI Tech Ltd engineers have over 15 years in deploying & maintaining environmental monitoring systems in mines and tunnels globally.

Gas Detection Monitoring

Fixed gas detection systems are usually deployed in tunnels and mines and usually comprise of sensors for measuring many types of gases, both toxic and flammable. Typical gases being measured are as follows –

  • Oxygen (O2)
  • Methane (CH4)
  • CO2 (Carbon Dioxide)
  • CO (Carbon Monoxide)
  • H2S (Hydrogen Sulphide)
  • NO2 (Nitrogen Dioxide)

Other gases can be added and on some recent projects MTI Tech have supplied and integrated Benzene detectors for specific contaminated ground conditions.

As well as ‘live’ data from the sensors being recorded, it is important that STEL (Short Term Exposure Limit) and the TWA (Time Weighted Average) data is recorded and stored. The STEL and TWA datapoints are common for toxic gases.


The STEL is a limit value above which exposure to a chemical substance should not occur and usually relates to a 15 minute reference period. The aim of a STEL is to prevent adverse health effects and other unwanted effects due to peak exposure that may not be controlled by the application of an 8 hour TWA limit.


The TWA for the exposure to a chemical can be used when both the chemical concentration and time for exposure varies over time. It is thus used as the average exposure to a contaminant to which workers may be exposed without adverse effect over a period such as in an 8-hour day or 40-hour week (an average work shift). They are usually expressed in units of ppm (volume/volume) or mg/m3.

Airflow Monitoring

Ventilation and a supply of fresh air is critical in a confined space environment, such as a mine or a tunnel. A minimum fresh air supply of 0.3 m3/min. per person should normally be sufficient to maintain a respirable atmosphere. Additional ventilation should be provided where construction is to be used, to mitigate the effects of exhaust emissions and/or heat generated.

MTI Tech Ltd supply and integrate airflow monitoring sensors and control equipment into mines and tunnels. The data from these sensors can be integrated into the SCADA system for monitoring and control, for example switching on/off for additional fans etc.

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