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Diesel particulate matter: Monitoring and control improves safety and air quality 209

11.7.5 Use of PPE

The use of PPE is a “last line of defense” to control miners’ exposure to DPM. It has
been estimated that in about 20% of all work institutions, 5% of all US workers wear
respirators during some of their job time [17]. Two types of respirators are generally
used to protect workers from gaseous and particulate pollutants: (a) air-purifying
respirators (APRs) purify air by removing and blocking contaminants from the air,
and (b) air-supplying respirators (ASRs) supply clean, pollutant-free air from another
source. Although respirators are effective in reducing mines’ exposure to DPM and
other mine air contaminants, they should be used after executing all other possible
available controls.

11.8 Summary and conclusions

DPM-related issues are currently high profile in underground mines worldwide.
A number of DPM control measures and ambient monitoring approaches are currently
practiced in underground mines. Although shift average-based DPM monitoring tech-
niques have been available for some time, these approaches do not help in gaining a
full understanding of DPM levels over short time periods. Real-time monitors can
almost instantly quantify DPM levels, produce data required for engineering assess-
ments, and provide detailed information about DPM levels for short- and long-term
intervals. Different DPM control technologies and strategies have proven to be effec-
tive in reducing miners’ exposure to diesel engine exhaust. The most effective
approach to control DPM in mines is the adoption of multiple measures, since there
is no single measure that completely resolves the issue.
DPM regulatory compliance is a big challenge especially in large underground M/
NM mines. In the US, DPM regulations are different for underground coal and M/NM
mines. For regulatory compliance, coal mine operators must add a certain amount of
fresh air in the mine before adding even a single diesel engine, whereas M/NM mine
operators must ensure the presence of good-quality breathing air in all working areas
of a mine. Under existing regulatory arrangements, MSHA does not require air quality
monitoring in underground coal mines. The expectation is that the addition of a
specific amount of fresh air in the mine will provide good-quality breathable air; how-
ever, exceptions can occur in the presence of short circuiting and recirculation. In such
cases, the addition of fresh air in the mine cannot guarantee good quality air. Although
MSHA does not currently measure air quality in underground coal mines, it seems
likely that underground coal mines may need to adopt M/NM DPM rules in order
to ensure suitable air quality.

References

[1] Cantrell B. In: Source apportionment analysis applied to mine dust aerosols: coal dust and
diesel emissions aerosol measurement. Proceedings 3rd mine ventilation symposium,
SME, Littleton, CO, USA; 1987. p. 495–501.
[2] Mody V, Jakhete R. Dust control handbook. Park Ridge, NJ, USA: Noyes Data Corpora-
tion; 1989. 203 pp.