Mining: Gas Detection and the Standards on No2 Exposure
Diesel exhaust and blasting fumes can contain nitrogen dioxide (NO₂), a toxic gas that can harm workers’ lungs. In underground mines, ventilation helps clear these contaminants. Gas monitoring helps mine teams assess worker exposure and check conditions in areas where NO₂ may accumulate.
In the mining industry, diesel engines produce nitrogen monoxide (NO), a combustion byproduct. In the presence of air, NO reacts almost immediately with oxygen to create NO2. Except for certain drilling equipment and specialized applications, most mechanized equipment used in metal mines nowadays is powered by diesel engines. Blasting also is at the origin of NO2 production. During a blast, all explosive materials create a cloud of reactive substances – and the most toxic of them is the NO2.
In Canada, The generally acceptable limit is of 3 parts per million (ppm). However, a recent trend aims at reducing this level at 0.2 ppm – a value fifteen times inferior to the value used in the past.
What are the health effects of NO₂ exposure?
Breathing NO₂ can irritate the eyes, nose and throat and cause coughing, chest pain or shortness of breath. High exposure can cause fluid to build up in the lungs, and serious symptoms can develop hours after exposure. Use gas monitoring to assess exposure, since odour is an unreliable indicator of concentration.
The human olfactory perception threshold for NO2 is between 0.1 and 0.2 ppm, depending on the conditions. That’s why portable instruments equipped with integrated NO2 sensors are becoming increasingly important inside mines.
NO2 contributes to respiratory problems, high bronchial reactivity and bronchial sensitivity to microbial infections. Prolonged exposure to high levels of nitrogen dioxide can cause irreversible damages to the respiratory system. Exposure to liquefied gaseous NO2 (high concentration) can cause severe burns to the skin, eyes and respiratory tract.
Complying with the standards
The first step is to determine the NO2 levels to check that the work environment complies with the regulations in force. It includes the validation of the environments after blasting, ventilation verification and exposure evaluation of high-risk workplaces.
It is essential to identify and eliminate the most important NO2 sources. For example, it can include the identification of the most polluting engines and to take corrective actions to limit NO2 emissions.
- Analysis of the actual NO2levels
- Identify and eliminate NO2sources
- Continuous monitoring of the environment
After taking corrective actions, it is necessary to continuously monitor the environment, particularly in areas where workers are more likely to be exposed to NO2, such as miners working with or near diesel engines in poorly ventilated areas or near tailing collection or grinding operations.
How can mines control and monitor NO₂ exposure?
Assess worker exposure. Identify tasks and locations where NO₂ can accumulate. Use representative breathing-zone measurements to assess worker exposure and area monitoring to track conditions at specific locations.
Reduce emissions and maintain ventilation. Maintain diesel engines and exhaust systems, and verify that ventilation can dilute and clear contaminants where equipment operates.
Verify conditions before re-entry after blasting. Follow the mine’s written re-entry procedure, including applicable ventilation and atmospheric testing requirements. Blasting can release multiple contaminants, including NO₂ and carbon monoxide.
How do you choose a gas detector for mining operations?
Start with the site’s hazard assessment. Choose a detector with sensors for the gases you need to monitor and verify that the NO₂ sensor’s range and resolution suit the concentrations you need to measure. Select the configuration for the job, whether it’s personal monitoring, area monitoring or remote sampling. Follow the manufacturer’s instructions for bump testing and calibration.
For the protection of miners against toxic gases, trust Dräger!
Based on its extensive experience in the mining industry around the world, Dräger has developed an efficient and well-known solution using products that contribute to the precise monitoring of NO2 levels in work environments, compiling the data to validate compliance with the standards.
Optimized for individual protection, the compact X-am 5000 personal monitor can measure up to five gases, can be configured to meet the specific needs of mining operations by selecting from 30 different electrochemical sensors. The X-am 5600 is an infrared personal monitoring device capable of detecting up to six different gases. Both instruments are compatible with the Dräger X-zone® to ensure optimal area monitoring.
In addition to multi-gas detectors, Dräger also offers products to collect data for monitoring and compliance purposes, as well for ventilation monitoring.
