Gas monitoring for tunnels and underground

A confined space is a closed or partially closed structure and most of severe or lethal accidents that occur while entering these areas are linked to combustible gas, toxic or asphyxiating (lack of oxygen) gases. These will be the main risks to evaluate within a gas monitoring safety process for tunnels and underground work using portable gas detectors and area gas monitors.

Chronic exposure to exhaust gases can cause severe neurological disorders (headaches, dizziness, irritability, drowsiness, convulsions), bronchial irritations or even lungs cancer in some cases. It is thus essential to permanently measure and control TWA (time weighted average) and STEL (short term exposure limit) exposure values in road and railroad tunnels for:

• Carbon monoxide
• Carbon dioxide
• Nitrogen oxides (nitric oxide and nitrogen dioxide)
• Sulphur dioxide
• Volatile organic compounds (VOC) including benzene
• Oxygen defficiency

Concerning personal protection, a multigas detector remains essential and indispensable. In addition, a area gas monitor will secure the working area. For very long tunnels, it will be advisable to use units with communication solutions as explained below…

Particularly suitable for tunnels, the LENS™ Wireless technology is a new way to approach safety. With this technology, once a detector or an area gas monitor enters in alarm following a gas hazard, a « man in distress » alarm or a panic situation, every paired detector will get instant alert.

⇒ More on the LENS Wireless technology

Self-rescuer masks a respiratory protective devices especially designed for emergency evacuation in non-breathable atmosphere – poorly oxygenated, smoky or extremmely toxic areas – for use when an air purifying respirator would be unefficient or hazardous. They originally have been designed for emergency evacuations from mines or long tunnels.

The most commonly used and the most cost-effective unit for confined space applications is the 4 gas detector (combustible gases, O2, CO and H2S). Yet for tunnels it advisable to use a multigas detector with CO-CO2-NO-NO2-O2 sensors. In order to ensure that the cells function correctly, a bump test is recommended before each use. For emergency evacuation, a self-rescuer respirator remains indispensable!