DPM Control Measures: How to Reduce Diesel Exhaust Exposure at Your Workplace

Diesel particulate matter (DPM) is a known carcinogen with no safe exposure threshold. This simple fact has one crucial implication: preventing exposure is not optional—it is mandatory.

The Work Health and Safety Act 2011 (Cth) requires Australian workplaces to systematically reduce hazardous exposures using the hierarchy of controls. Health effects of DPM exposure. For DPM, this hierarchy is not a suggestion or a framework for selecting between options of equal merit. It is a legal requirement to pursue controls in a specific order, prioritizing elimination and substitution before resorting to engineering or personal protective equipment.

Many Australian workplaces default to the lowest tiers of the hierarchy—PPE and administrative controls—because they appear cheaper than elimination or substitution. This is short-sighted and legally indefensible. Modern technologies now exist to dramatically reduce or eliminate DPM exposure. The investment is significant, but the return—in worker health, regulatory compliance, and reduced workers’ compensation costs—far exceeds the cost.

This article explains how to apply the hierarchy of controls to DPM exposure and provides practical strategies tailored to Australian workplaces. We also cover an emerging and largely unrecognized control strategy: battery electric vehicles (BEVs) in underground mining and tunnelling, which represents a genuine paradigm shift in how we approach occupational diesel exposure.

The WHS Hierarchy of Controls Applied to Diesel Exhaust

The hierarchy of controls is a tiered approach to hazard management:

1. Elimination — remove the hazard entirely
2. Substitution — replace the hazard with something safer
3. Isolation — physically separate workers from the hazard
4. Engineering controls — install or modify equipment to reduce the hazard
5. Administrative controls — change work practices to reduce exposure
6. Personal protective equipment (PPE) — provide protection to individual workers

Each tier is more effective and more reliable than the one below it. Elimination eliminates risk entirely. Substitution significantly reduces risk. Isolation and engineering controls reduce risk substantially. Administrative controls and PPE are important backup measures but are inherently less reliable because they depend on consistent human behavior.

For DPM, this hierarchy is not merely theoretical—it is the only pathway to achieving the new December 2026 workplace exposure limit of 0.01 mg/m³ in many Australian workplaces. Let’s examine each tier.

Level 1 — Elimination: Removing Diesel from the Equation

Elimination is the gold standard of hazard control. For DPM, elimination means removing diesel-powered equipment entirely and replacing it with zero-emission alternatives.

For many decades, elimination was technically infeasible in certain high-duty applications, particularly in underground mining and tunnelling. Diesel equipment provides high torque, extended operating hours without refueling, and proven reliability in harsh environments. Battery technology simply wasn’t there.

This has changed.

Battery Electric Vehicles (BEVs) in Underground Mining

Over the past 5 years, major global mining equipment manufacturers—Caterpillar, Sandvik, Epiroc, and others—have released battery electric versions of underground loaders, drill rigs, and utility vehicles. These are not prototypes or niche products. They are production machines entering service in mines globally.

Why BEVs matter for DPM control:

• Zero tailpipe emissions — BEVs produce no diesel exhaust whatsoever, eliminating DPM at the source
• Comparable performance — modern BEVs match or exceed diesel equipment in torque, load capacity, and duty cycle
• Operational cost advantage — electricity is significantly cheaper than diesel fuel; maintenance costs are lower due to fewer moving parts
• Underground ventilation benefits — eliminating diesel equipment reduces the total ventilation load required in underground mines, allowing for smaller, less expensive ventilation systems
• Regulatory alignment — BEVs make achieving the December 2026 WEL genuinely feasible without relying on complex engineering controls or respiratory protection

Adoption barriers in Australian mining:

Despite these advantages, BEV adoption in Australian underground mining has been slower than in Scandinavian or Canadian mines. Key barriers include:

1. Capital cost — BEV equipment typically costs 15–25% more than diesel equivalents (though total cost of ownership favors BEVs)
2. Charging infrastructure — mines must invest in underground charging stations
3. Regulatory uncertainty — Australian mining regulations are still being updated to reflect BEV realities (e.g., thermal management in confined spaces, battery safety in underground environments)
4. Workforce familiarity — operators trained on diesel equipment require retraining for BEVs

However, the economic and regulatory trends strongly favor BEV adoption. As the December 2026 WEL deadline approaches, mines that have not begun transitioning to BEVs will face mounting pressure to do so to achieve compliance.

Electric Equipment in Other Industries

Beyond mining, electric alternatives exist for many diesel applications:

• Forklift trucks: Lithium-ion electric forklifts are mature, cost-effective, and widely available
• Pumps and generators: Grid-connected power or battery-backed electric generators eliminate diesel gensets in many scenarios
• Portable compressors: Electric compressors are feasible for construction and trade applications
• Port equipment: Electric reach stackers and container handlers are now deployed at major ports

Elimination should always be the first question asked: Can we eliminate diesel equipment entirely from this application? If the answer is yes, elimination is not an option—it is your regulatory obligation.

Level 2 — Substitution: Low-Emission Fuels and Cleaner Equipment

When elimination is not feasible, substitution is the next tier. This means replacing diesel with a lower-emission fuel or replacing aging diesel equipment with newer, cleaner equipment.

Fuel Substitution: Liquefied Petroleum Gas (LPG) and Ultra-Low-Sulphur Diesel

Liquefied Petroleum Gas (LPG):

LPG burns more cleanly than diesel, producing significantly lower particulate emissions. In industries where diesel engines are essential but electric alternatives are not yet viable, LPG-powered equipment can reduce DPM emissions by 50–70%.

However, LPG has limitations:
– Not all equipment types are available with LPG engines
– Requires safe fuel storage and handling infrastructure
– Energy density is lower than diesel, reducing operating range for some applications
– Cost premiums can be significant

Ultra-Low-Sulphur Diesel (≤10 ppm sulphur):

Ultra-low-sulphur diesel burns more cleanly than conventional diesel and reduces particulate emissions by 30–40% when used in modern engines. This is a straightforward substitution that requires no equipment changes—merely sourcing cleaner fuel.

The limitation is obvious: it reduces DPM emissions but does not eliminate them. Ultra-low-sulphur diesel is a stepping stone toward elimination, not a final solution.

Equipment Age and Tier Classification

Diesel engines are classified by emissions tier, reflecting the regulatory era in which they were manufactured:

• Tier 1 engines (pre-2006): Highest particulate emissions
• Tier 2 engines (2006–2011): Moderate particulate emissions
• Tier 3 engines (2011–2014): Reduced particulate emissions
• Tier 4 Interim engines (2014–2015): Significant particulate reduction
• Tier 4 Final engines (2015–present): ≥90% lower particulate emissions compared to Tier 1

Tier 4 Final engines achieve their low emissions through a combination of advanced combustion technology, fuel injection refinement, and onboard diesel particulate filters.

Practical substitution strategy: If diesel equipment cannot be eliminated, progressively replace aging Tier 1 and Tier 2 equipment with Tier 4 Final equipment. While still not zero-emission, Tier 4 Final equipment can achieve exposures that approach the new 0.01 mg/m³ limit when combined with proper ventilation and isolation.

Level 3 — Isolation: Separating Workers from Diesel Exhaust Sources

When elimination and substitution reach their limits, isolation becomes critical. Isolation means physically separating workers from diesel exhaust sources, allowing diesel equipment to operate while minimizing worker exposure.

Operator Cabs with Positive Pressure Ventilation

Modern diesel-powered underground vehicles can be fitted with operator cabs featuring positive-pressure filtration systems. Fresh air is drawn into the cab, filtered through HEPA-grade filters to remove DPM, and maintained at slight positive pressure to prevent exhaust infiltration.

Effectiveness: Properly installed and maintained positive-pressure cabs reduce operator exposure by 60–85%.

Limitations: This approach protects operators but not other workers in the vicinity. Passive exposure in a decline or tunnel near diesel equipment remains significant.

Separation of High-Emission Zones

In underground operations, scheduling can separate workers from high-emission activities. For example:

• Operate high-emission equipment (e.g., production drilling) during shifts when fewer workers are present in the affected area
• Rotate workers through high-exposure roles so no single worker accumulates excessive exposure
• Physically separate administrative and lower-exposure workers from active diesel-powered equipment zones

Ventilation as Isolation

Ventilation is partly isolation and partly engineering control. By directing fresh air toward workers and extracting contaminated air away from work zones, ventilation creates physical separation between workers and DPM sources.

Enhanced ventilation in underground mining—using fans, ducting, and strategically placed air outlets—is a proven isolation strategy. However, ventilation has limits: if DPM sources are not reduced through elimination or substitution, ventilation demands become enormous and energy costs become unsustainable.

Level 4 — Engineering Controls: DPFs, DOCs, Ventilation Systems

Engineering controls modify equipment or install systems that reduce hazardous emissions without removing the hazard source entirely.

Diesel Particulate Filters (DPFs)

Diesel particulate filters trap DPM particles before they enter the atmosphere. Exhaust gases pass through a filter media (ceramic or sintered metal), and particulates deposit on the filter surface. Periodically, the filter undergoes regeneration—either active (using an electric heater or catalyst) or passive (relying on high exhaust temperatures)—burning off accumulated soot.

Effectiveness: DPFs reduce particulate emissions by 85–99% when functioning correctly. They are extraordinarily effective.

Limitations and considerations:

1. Regeneration failures — if passive regeneration doesn’t occur (e.g., during low-load operation), filter loading increases and back-pressure builds, eventually requiring manual intervention
2. Active regeneration energy — active DPF systems require additional fuel or electricity to maintain regeneration cycles
3. Maintenance burden — filters must be monitored, serviced, and replaced according to manufacturers’ schedules
4. Cost — DPF retrofit installations on older equipment can be expensive

For underground mining, DPF retrofits on existing diesel equipment are increasingly standard. Modern mining vehicles come equipped with DPFs from the factory.

Diesel Oxidation Catalysts (DOCs)

DOCs use a catalytic substrate to chemically oxidize hydrocarbons and carbon monoxide in diesel exhaust, reducing emissions. They are less effective at removing fine particulates than DPFs but can reduce overall particulate emissions by 50–60%.

DOCs are simpler, cheaper, and more robust than DPFs, making them suitable for retrofitting older equipment. However, they are less effective and do not achieve the particulate reductions possible with modern DPFs.

Exhaust Gas Recirculation (EGR)

EGR systems return a portion of exhaust gases back into the combustion chamber, lowering combustion temperatures and reducing particulate formation. This is primarily a manufacturing innovation found in modern Tier 3 and Tier 4 engines, though it can be retrofitted to some older equipment.

EGR reduces particulate emissions by 20–40%, depending on the system design and operating conditions.

Ventilation Systems: The Engineering Foundation

In underground environments, engineered ventilation is the single largest factor determining DPM concentrations at worker breathing zones.

Principles of effective ventilation:

1. Supply air volume — must be sufficient to dilute DPM to acceptable concentrations; typically 6 air changes per hour minimum in diesel-heavy underground operations
2. Directional flow — air should flow from clean areas toward contaminated areas, with extraction points positioned to capture diesel exhaust at the source
3. Thermal stratification — in deep underground, temperature gradients affect air flow; ventilation design must account for buoyancy effects
4. Equipment spacing — distance between diesel equipment and workers affects exposure; greater separation allows more dilution

Upgrading ventilation systems is often the most cost-effective engineering control in established underground operations. Larger fans, additional ducting, or repositioned air outlets can reduce DPM concentrations by 30–60% without equipment modifications.

Level 5 — Administrative Controls: Work Practices That Reduce Exposure

Administrative controls modify work practices to reduce exposure without eliminating or substituting hazards.

Idling Restrictions

Diesel equipment produces maximum emissions when idling. A simple administrative control: prohibit unnecessary idling. Operators should shut down equipment during breaks rather than leaving engines running.

In underground mining, this means:
– No warm-up idling before shift start (warm up while moving)
– Shut down during meal breaks
– Immediate shutdown after completing tasks rather than waiting in equipment

This straightforward practice reduces DPM emissions by 10–20% in facilities where idling discipline is weak.

Work Rotation

Rotating workers through different roles can reduce cumulative exposure to any single individual. For example:
– Loader operators work 4 hours in the high-exposure loader role, then 4 hours in lower-exposure tasks
– Drill operators are rotated away from the drill site at midshift

Work rotation is ethically important—it prevents overexposure of individual workers—but it is not a primary control strategy. It should complement, not replace, engineering and substitution controls.

Scheduling High-Emission Tasks

Scheduling high-emission activities (e.g., bulk explosives loading, intensive drilling) during shifts with fewer workers present reduces population-level exposure. This requires coordination with production planning but is practical in many operations.

Exposure Notification Systems

Workers should be informed of their exposure levels. Providing real-time or regularly updated DPM concentration data from work areas raises awareness and encourages behavior changes that reduce exposure.

Level 6 — PPE: When Respiratory Protection Is the Last Line of Defence

Personal protective equipment—specifically, fitted P2/N95 respirators—is the final control tier. Respirators are critical as a backup measure but should never be the primary control strategy for occupational carcinogen exposure.

P2 Respirators: Effectiveness and Limitations

P2 respirators filter at least 94% of inhaled air, removing DPM and other particulates. When properly fitted and consistently worn, they reduce inhalation exposure by approximately 15-fold (from an unprotected baseline).

However:

1. Fit testing is mandatory — from December 2026, workers using respirators for DPM protection must undergo annual fit testing to ensure the respirator seals properly around the face
2. Consistency is critical — respirators are only effective if worn correctly during the entire exposure period; any gap in the seal compromises protection
3. Not all exposure is inhalation — some DPM components may be absorbed through skin or ingested; respirators only address inhalation
4. Worker compliance issues — in hot, humid underground environments, wearing respirators continuously is uncomfortable and compliance often falters
5. False security — the presence of a respiratory protection program can create a false sense of security, potentially delaying investment in more reliable engineering controls

Respirator Requirements from December 2026

From December 1, 2026, the Australian Standard AS/NZS 1715:2009 will require:

• Mandatory fit testing before first use, then annually
• Proper assignment of respirator type based on hazard concentration and exposure scenario
• Medical clearance from an occupational health professional confirming workers are medically suitable for respirator use
• Regular training on proper donning, doffing, and use procedures

These requirements exist because regulators recognize that respirators are a serious, high-responsibility control measure, not a simple “wear a mask” solution.

Post-Control Monitoring: Verifying Your Controls Are Working

Installing controls is not sufficient. DPM monitoring program. You must verify that controls are actually achieving their intended effect through post-control monitoring.

Baseline Assessment

Conduct a baseline DPM exposure assessment before implementing new controls. Exposure assessment to identify risks. This establishes your starting point and provides a reference against which to measure improvement.

Post-Implementation Re-Testing (3-Month Window)

After implementing new controls (DPF retrofits, ventilation upgrades, BEV introduction, etc.), conduct a follow-up exposure assessment within 3 months. This assessment must:

• Sample the same worker roles and locations as the baseline
• Use the same sampling methodology (personal air sampling via gravimetric or optical analysis)
• Compare results to baseline to quantify the exposure reduction achieved
• Identify any work areas or worker roles where controls were inadequate

If post-control levels exceed the December 2026 WEL of 0.01 mg/m³, additional controls must be implemented.

Ongoing Monitoring

After verifying control effectiveness, establish an ongoing monitoring frequency based on risk level:

• High-risk sites (exposure >0.05 mg/m³ baseline): quarterly monitoring
• Moderate-risk sites (exposure 0.01–0.05 mg/m³): semi-annual or annual monitoring
• Low-risk sites (exposure <0.01 mg/m³): biennial monitoring

Monitoring verifies that controls continue to function and that changes in operations have not degraded protection.

Building a DPM Control Plan: A Practical Framework

Systematic DPM control requires a comprehensive control plan. Here’s a practical framework:

Step 1: Baseline Assessment (Month 1)

Conduct personal air sampling at all exposed worker locations. Classify risk level (low, moderate, high) based on results.

Step 2: Hierarchy Application (Month 2–3)

For each exposed work area:
– Assess feasibility of elimination (BEVs, electric equipment)
– Assess feasibility of substitution (LPG, Tier 4 equipment)
– Identify isolation opportunities (ventilation, operator cabs, scheduling)
– Plan engineering controls (DPFs, exhaust capture, ventilation upgrades)
– Plan administrative controls (idling restrictions, work rotation)
– Plan PPE program (fit testing, medical clearance, training)

Step 3: Control Implementation (Month 4–12)

Prioritize high-impact, feasible controls. Install DPFs and ventilation upgrades before respirator programs.

Step 4: Post-Control Assessment (Month 3–4 after implementation)

Re-test at exposed worker locations to verify control effectiveness.

Step 5: Ongoing Monitoring Program (Ongoing)

Establish frequency based on risk profile and historical results.

Step 6: Review and Iteration (Annually)

Review monitoring results, equipment performance, and operational changes. Adjust controls as needed.

FAQ: Common Questions About DPM Control Measures

Q: If we install DPFs on all our diesel equipment, can we avoid the December 2026 WEL problem?

A: DPFs are highly effective (85–99% particulate reduction), but their effectiveness depends on proper maintenance and operation. In underground mining with heavy equipment, DPFs alone may achieve the 0.01 mg/m³ WEL if combined with adequate ventilation, but this cannot be assumed without post-control monitoring. Many Australian workplaces will need to combine DPFs with at least one additional control measure (ventilation upgrades, equipment substitution, or elimination) to reliably achieve the new limit.

Q: How much does it cost to retrofit DPFs on existing diesel equipment?

A: Retrofit costs vary widely depending on equipment type and local labor costs. Typical costs range from $5,000 to $50,000 per vehicle, with larger earthmoving or mining equipment at the higher end. However, fuel savings and reduced maintenance often recover this cost within 3–7 years. More importantly, the cost of retrofitting must be weighed against the cost of managing occupational disease claims (often exceeding $1 million per claim) and regulatory penalties.

Q: Are battery electric vehicles really practical in underground mining?

A: Yes, increasingly so. Modern BEVs from Caterpillar, Sandvik, and Epiroc have proven themselves in production mining in Canada, Scandinavia, and Australia. Challenges include initial capital cost, charging infrastructure, and regulatory adaptation, but none are insurmountable. The trend globally is clearly toward BEV adoption in underground mining. Australian mines that begin transitioning now will have competitive advantages in recruitment, regulatory compliance, and operating costs.

Q: Can we meet the December 2026 WEL using only ventilation and PPE?

A: Theoretically yes, but not practically or sustainably. Ventilation requirements to achieve 0.01 mg/m³ in high-diesel-emission environments (e.g., intensive tunnelling) would demand enormous air volumes, enormous power consumption, and correspondingly enormous capital and operating costs. PPE (respirators) alone provides only ~15-fold reduction, insufficient for many high-exposure scenarios. The regulatory intent of the hierarchy of controls is to drive elimination and substitution—the most reliable, sustainable solutions—rather than relying on ventilation and PPE indefinitely.

Q: If we’ve used control measures for years and exposure is below the current limit, do we need to change anything for December 2026?

A: Likely yes. The new limit is 10 times stricter than the previous one. If your current exposure is 0.05 mg/m³ (previously acceptable), it will be non-compliant from December 2026. You should conduct a baseline assessment immediately to understand your current exposure level relative to the new limit, then plan additional controls if necessary.

Q: How do we know which control measures will work best at our specific workplace?

A: This requires site-specific exposure assessment and feasibility analysis. Every workplace is different—geology, equipment mix, ventilation capacity, production goals, and budget vary widely. Professional occupational hygiene assessment can identify which controls are most cost-effective at your site. This is where specialized expertise makes a genuine difference.

Conclusion

The WHS hierarchy of controls provides a clear pathway to reducing DPM exposure from dangerous levels to below the December 2026 limit. The pathway begins with elimination (BEVs, electric equipment), progresses through substitution and isolation, and only defaults to engineering controls, administrative controls, and PPE when the higher tiers are exhausted.

Too many Australian workplaces remain stuck in old patterns of thinking: diesel equipment is necessary, exposure control means ventilation and respirators, and health risk is just an unavoidable cost of doing business. This thinking is outdated and legally indefensible.

Modern technologies now offer genuine alternatives to diesel. Investment in BEVs, DPFs, and enhanced ventilation is substantial, but it is far less costly than managing occupational cancer claims, regulatory penalties, and the moral burden of knowing workers developed preventable disease under your watch.

After implementing controls, monitoring verifies their effectiveness and ensures ongoing compliance. At Anitech Group, we help Australian workplaces design and implement comprehensive DPM control plans, conduct post-control assessments, and establish monitoring programs that verify protection.

Book a post-control DPM assessment with Anitech Group to verify your controls are working.