Hazard, limit and sensor — on one table
The GN 6053 amendment — published 28 March 2025 and, according to published summaries, applied from 1 June 2025 — lowered several airborne-pollutant limits; the silica figure is the one every mine has had to re-baseline against.
| Hazard | Limit / milestone | Real-time sensor | Personal sampling role |
|---|
| Respirable crystalline silica | 0.05 mg/m³ OEL (was 0.1); the 2024 MHSC milestone review set 95% of results below 0.03 mg/m³ by December 2034 (the 2014 milestone had been 0.05 by 2024) | Optical particulate monitors at fixed points and on machines | Gravimetric + XRD remains the compliance measurement; real-time finds the sources |
| Respirable coal dust | Per OEL regulations (amended 2025) | Optical particulate monitors | Compliance sampling |
| Carbon monoxide | Per OEL regulations | Electrochemical fixed and wearable | Spot checks at headings |
| Nitrogen dioxide (diesel) | Per OEL regulations | Electrochemical, near diesel fleet routes | Diesel-area sampling |
| Methane | Withdrawal thresholds per the mine's ventilation and gas plan | Catalytic / infrared with trip logic | Continuous — this is a life-safety interlock, not a hygiene sample |
| Diesel particulate matter | Per OEL regulations | Elemental-carbon surrogate monitors | Personal sampling |
| Noise | MHSC: equipment ≤107 dB(A) by Dec 2024, ≤104 dB(A) by Dec 2034; no new NIHL cases by 2034 | Fixed noise loggers per area and per machine | Personal dosimetry for exposure |
| Heat | Per the mine's heat-stress management programme | Wet-bulb / globe temperature at working places | Physiological monitoring where required |
How to start
- Rank hazards by risk. Use your existing risk assessments and medical surveillance trends to identify your worst hazard — often respirable silica, DPM or heat — and your worst section.
- Start there, real-time. Deploy continuous monitoring for that one hazard in that one area, with alarms set to your occupational exposure limits.
- Connect it to a response. An alarm must drive an action — ventilation on, sprays on, withdraw, investigate — with a named owner. Data without a response changes nothing.
- Prove a control works. Measure the before-and-after of one intervention to demonstrate the value and build internal buy-in.
- Integrate and expand. Bring the data into one platform alongside your other safety systems, then extend to the next hazard and section.
- Design for the underground. Sensors rated for dust, humidity and intrinsic safety where required, on a communications backbone that reaches the working places.
This is part of addanode's mining operations optimisation solution: real-time dust, gas, DPM, noise and heat monitoring on one addaNet platform, alongside person location and collision prevention — so environmental health, safety and compliance data live in one picture and one record. Because we build both the hardware and the software in-house and support it locally, monitoring can share the same underground backbone and control room as your other safety systems, engineered for real South African conditions.
This guide is general orientation; always confirm current occupational exposure limits, definitions and obligations against the latest Mine Health and Safety Act, its regulations and your appointed occupational hygienist and legal advisers.
Frequently asked questions
What does occupational hygiene monitoring measure in a mine?
The cumulative health hazards of the working environment: respirable dust (especially silica and coal), gases such as CO, methane and NO₂, diesel particulate matter (DPM), noise, and heat and humidity. These are the exposures that cause occupational lung disease, hearing loss and heat illness over time — distinct from immediate safety hazards like collisions.
Why move from spot sampling to real-time monitoring?
A spot sample captures one location at one moment and is read days later in a lab — it can't warn anyone in real time and misses the short, severe exposure peaks that do the damage. Continuous monitoring sees exposures as they happen, lets you act before a limit is breached, and builds a defensible record for MHSA compliance and medical surveillance.
Does real-time monitoring replace personal sampling and our occupational hygienist?
No — it complements them. Continuous area and personal monitoring give live coverage and catch peaks between formal sampling campaigns, while your occupational hygienist interprets the data, sets the strategy and signs off compliance. The technology widens coverage; the professional judgement still governs.
Which hazard should we monitor first?
Start with your highest-risk hazard in your highest-risk section, guided by your existing risk assessments and medical surveillance trends — commonly respirable silica, DPM or heat stress. Prove the value there with alarms tied to a real response, then expand to the next hazard and area.
Can hygiene monitoring run on the same system as our other safety tech?
Yes, and it's more effective that way. Running dust, gas, DPM, noise and heat monitoring on the same platform and underground backbone as person location and collision prevention gives you one safety picture, one control room and one compliance record — rather than several disconnected systems to maintain and reconcile.
Want to see exposures as they happen?
Tell us your priority hazard and your toughest section. We'll help you deploy real-time monitoring where the risk is highest — with alarms tied to a response and a record that stands up to scrutiny.