Exhaust emissions are an important issue in the underground mining and tunnelling sectors because both make intensive use of diesel engines within a confined space.
In the case of underground work there is a requirement to keep the toxic elements of exhaust gas under control in order to safeguard the health of employees.
This is normally achieved by a combination of forced ventilation and reduction at source, however forced ventilation is expensive to install and run and therefore it makes sense to reduce emissions at source first.
The aim is to ensure that the working environment is as pleasant as possible, visibility is good, and the pollutants emitted by the engine are well within the limits which apply.
These may be statutory, for example they may be set out in a law which deals with occupational health, or a condition of a contract.
Frequently in the tunnelling sector, contracts incorporate the recommendations of the British Tunnelling Society as regards exhaust emissions, and this imposes a very low limit for nitrogen oxides (nox).
A variety of standards are applied in the underground mining industry, for example those devised by the Mine Safety & Health Administration (MSHA).
A similarity between the mining and tunnelling sectors is that both make use of specialised machinery which is expensive to replace but has a long economic life.
For this reason it often makes financial sense to upgrade the exhaust emission control system to incorporate the latest technology.
(Photo: Schoma tunnelling locomotive fitted with diesel particulate filter)