Working in oxygen-deficient atmospheres

Background

Recently, mine workers in a light vehicle entered a section of a mine where the ventilation flow through the area had been interrupted. The vehicle was unable to reverse up a decline to exit the affected area, resulting in the workers exiting by foot.

As a consequence, workers experienced symptoms of oxygen deprivation, including light-headedness and an increased breathing rate.

The area of the mine had previously been backfilled with waste rock, and associated infrastructure (including pumps) was removed. The area was dependent on natural airflow ventilation.

The geometry of the mine in the backfilled area meant rising water levels could interrupt the ventilation flow through the working section.

The lack of ventilation was not detected and no workers wore self-rescuers when exiting the area on foot.

It was not realised the oxygen-deficient atmosphere could have a negative impact on the vehicle engine power and result in poor engine performance.

Control measures

Before work starts in underground environments, ensure:

• work is planned so it can be done safely, including the maintenance of recommended levels of ventilation during and after the abandonment of mine working areas
• consideration is given to the removal of dewatering or associated infrastructure, that may have the potential to impact primary ventilation flow
• workers are aware of mine ventilation standards and requirements
• gas monitoring information and training is made available to workers for early detection of harmful gases or low oxygen levels when re-entering unventilated areas
• the potential for hazardous atmospheres are identified during the safety assessment process, and comprehensive control measures are implemented and functional.

When undertaking work in underground environments, ensure:

• active mine workings are routinely inspected
• gas monitoring information and training is made available to workers for early detection of harmful gases or low oxygen levels when re-entering unventilated areas
• workers are competent in the use of self-rescuers and trained in hazard identification
• there is a system to ensure all unused and unventilated workings are barricaded to prevent unauthorised access and control hazards of re-entry into the area.