RS20: Dust Control in Surface Coal Mines

Recognised Standard 20 covers dust control in surface mines. It supports the dust provisions of the Coal Mining Safety and Health Regulation 2017 and provides the framework for a dust management plan across the dust generating processes at an open cut coal mine and the surface areas of an underground mine. It applies to all activities at a surface coal mine.

This guide covers the exposure limits that apply, where the dust actually comes from on an open cut, what a dust management plan needs to contain, and why the monitoring result is only half the obligation.

The exposure limits

From 1 September 2020 the occupational exposure limits in Queensland coal mining are 1.5 mg/m³ for respirable dust and 0.05 mg/m³ for respirable crystalline silica, both as eight hour time weighted averages.

The silica limit is the one that changes behaviour. At 0.05 mg/m³ it is low enough that ordinary open cut activities in the wrong material can approach it, and it is low enough that the sampling has to be done properly to mean anything. Overburden with high quartz content, drilling in sandstone, and dry haul road surfaces in the wrong season are all capable of producing exceedances that would not have registered against the older limits.

An exposure limit is a ceiling, not a target. The obligation under the Act is to hold risk at an acceptable level, which means as low as reasonably achievable, not just under the number. A site sitting consistently at 90 per cent of the limit and treating that as compliance has misread the obligation, and this is exactly the reasoning covered in acceptable level of risk and what you can prove.

Where the dust actually comes from

The mental model of open cut dust is usually a haul road on a windy day. Roads matter, and they are not the whole picture.

• Haul roads and light vehicle roads. The largest single source on most operations, driven by surface material, moisture, traffic volume and speed.
• Drilling. Concentrated, close to the operator, and the highest silica risk on most sites depending on the strata.
• Blasting. Short duration, high volume, and the source most likely to leave the lease.
• Loading and dumping. Drop height and material moisture do most of the work.
• Dozer and grader operations. Continuous, close to the cab, and often overlooked because the machine is enclosed.
• Coal handling and preparation. Conveyors, transfer points, stockpiles and reclaim.
• Wind erosion of exposed surfaces. Stockpiles, spoil, and any large area left bare and dry.

The point of listing them is that a dust management plan built around water carts is a plan that addresses one source and reports on all of them.

What a dust management plan needs

RS20 frames the plan around the dust generating processes rather than around the equipment. In practice a plan that survives an audit answers these, source by source:

• What generates dust here, and how much. Based on measurement, not assumption.
• What controls apply, in order of the hierarchy. Elimination and substitution first, engineering controls next, administrative controls after that, respiratory protection last and never as the primary control.
• Who is exposed, and in what similar exposure groups. Sampling a driller tells you nothing about a serviceman.
• What triggers a response and what the response is. A dust TARP with real trigger levels, in the same shape as the one described in building a trigger action response plan.
• How the controls are verified as working. Not whether they exist, whether they are effective.
• How results feed back into the plan. Monitoring that never changes anything is a data collection exercise.

Control measures that carry the load

Water is the default and it has real limits. Over watering a haul road creates a different hazard, degrades the running surface, and produces the corrugations and edge failure that RS19 road design is trying to prevent. The interaction between dust control and road condition is one of the more common places where two control systems work against each other.

• Surface treatment and chemical suppressants on high traffic roads, which reduce water demand and hold the surface together.
• Drill dust collection systems maintained as critical controls, not as an optional extra that gets bypassed when it blocks.
• Enclosed, pressurised and filtered cabs with a filter change regime that is actually tracked. A cab is only a control while its seals and filters are intact.
• Sequencing and scheduling. Not drilling upwind of a crew is free, and it is an engineering control in everything but name.
• Blast timing against meteorological conditions, which also serves fume management. See blast fume management in open cut mining.
• Rehabilitation and surface stabilisation of areas that are no longer active.

Monitoring, and where RS14 fits

RS20 is about control. RS14 covers the monitoring of respirable dust in coal mines. They are different standards addressing different halves of the same problem, and sites regularly cite one when they mean the other.

The practical relationship is that monitoring exists to tell you whether the controls in the dust management plan are working. A sampling programme that reports numbers to a health and hygiene function, with no defined path back into changing the controls, satisfies the monitoring obligation while leaving the control obligation unaddressed.

Health surveillance sits alongside both. It detects the consequence of exposure. It is not a control, and a site that treats clear health surveillance results as evidence that its controls are adequate has the logic backwards by several years, which is the time lag involved.

Where sites come unstuck

• The plan covers roads and little else. Drilling usually carries the highest silica exposure and gets the least attention in the plan.
• Similar exposure groups are wrong. Groups drawn from the org chart rather than from what people actually breathe produce sampling that is technically valid and practically meaningless.
• Controls are listed, not verified. The cab filter regime exists on paper, and nobody can say when the filters in unit 412 were last changed.
• Exceedances are managed as incidents rather than as plan failures. An exceedance says the control set was inadequate for those conditions. Investigating the person is easier and useless.
• Respiratory protection has quietly become the primary control. It is last in the hierarchy for good reasons, and it is the control most sensitive to fit, wear time and discipline.

Making the control evidence visible

The hard part of RS20 is not deciding what the controls should be. It is showing, on any given day, that they were in place and working across a lease measured in square kilometres.

HazView holds that against the ground. Dust controls are recorded where they apply, so a road section, a drill pattern or a stockpile carries its own inspection history with time, person and photographs attached. Verification checks on critical controls such as drill dust collection and cab filtration are assigned and tracked, and overdue ones are visible rather than found later. Conditions that trigger a dust response can be logged in the field by the person who saw them.

Monitoring results usually live in a hygiene system, and they should. The REST API lets those results come across and sit against the areas and activities they were taken from, so exposure data and control verification are looking at the same map instead of at each other across two reports. It also means the data can go back out to corporate reporting without anyone rekeying it.

The platform does not measure dust and does not assess exposure. Those are jobs for occupational hygienists and calibrated instruments. What it changes is whether the control half of RS20 can be demonstrated as readily as the monitoring half.

See how HazView works for managers, or book a demo.

Related guides

• Recognised Standards for Queensland Open Cut Coal Mines
• Blast Fume Management in Open Cut Mining
• Tailings Storage Facility Management
• RS11: Training in Coal Mines
• All QLD Open Cut Coal guides

Frequently asked questions

What is the respirable dust limit in Queensland coal mines?

1.5 mg/m³ for respirable dust and 0.05 mg/m³ for respirable crystalline silica, as eight hour time weighted averages, in force since 1 September 2020. Both are ceilings rather than targets.

Does RS20 apply to underground mines?

It applies to surface coal mines and to the surface areas of underground coal mines. Underground dust control is dealt with separately under RS15, and monitoring under RS14.

What is the difference between RS20 and RS14?

RS20 is about controlling dust. RS14 is about monitoring respirable dust. You need both, and satisfying the monitoring standard says nothing about whether your controls are adequate.

Is a dust management plan mandatory?

RS20 provides the framework for one as a way of achieving an acceptable level of risk for dust. As with any recognised standard you can take another approach, provided you can show it achieves at least the same level of control. In practice, no site has produced a more defensible structure than a documented plan.

Where does respiratory protection sit?

Last in the hierarchy of control, as a supplement to engineering and administrative controls rather than a replacement for them. It is also the control most dependent on fit testing, wear time and individual discipline, which makes it the hardest to verify as effective.