Three of the hazards that cause the most serious harm on site — noise, confined spaces and excavations — all have hard rules. Here are the numbers and the controls.
Noise — 85 dB(A)
The exposure standard is 85 dB(A) averaged over an 8-hour shift (LAeq,8h) plus a peak of 140 dB(C). A masonry consaw alone clears 100 dB(A). When you exceed the standard: eliminate at the source (quieter plant or process), then engineering (enclosures, isolation, maintenance), then admin (rotation, time limits, distance), then provide class-rated hearing protection — and run audiometric testing for workers required to frequently wear it. (See Occupational Hearing Loss for the long-term toll.)
Confined spaces — AS/NZS 2865
A confined space (under AS/NZS 2865) is an enclosed or partly enclosed space not designed to be occupied, where there is a risk of unsafe oxygen, harmful contaminants, or engulfment — pits, tanks, sewers, deep shafts, large pipes, some excavations. Before anyone enters, the PCBU needs:
- a documented risk assessment;
- atmospheric testing from outside before entry (oxygen, flammable gases, contaminants), plus continuous monitoring where conditions can change;
- controls — isolation and lock-out, purging, forced ventilation, ignition control, PPE/RPE;
- a written entry permit for each entry (the space, the authorised people, controls, gas results, duration), issued by a competent person and displayed at the entry;
- a rescue plan you can actually execute — with retrieval gear (tripod, winch, harness) and trained standby personnel; you cannot rely on emergency services for the primary rescue;
- trained workers, standby and spotters.
Excavations — over 1.5 metres
A trench deeper than 1.5 metres is high-risk construction work and needs an engineered collapse-prevention system plus a SWMS. The three methods: shoring (hydraulic or timber, trench shields, sheet piling), benching (stepped levels), or battering (sloping the sides to a safe angle for the soil). You also need a geotechnical assessment where required, located underground services, safe access and egress (ladders, ramps), edge protection and exclusion zones, atmospheric testing, and water-ingress control that does not undermine the excavation or nearby structures.
Before you dig — every time
WHS law expects you to get current underground-service plans before excavating, through Before You Dig Australia (BYDA) — the free national referral service: lodge the project area online, BYDA notifies the asset owners (power, gas, water, telco), and they send you plans and conditions. Treat BYDA plans as a starting point, not a permit to dig — you still have to physically locate services (cable locators, potholing, vacuum excavation) and hand-dig near them. In NSW the plans must be no more than 30 days old when you start.
Common mistakes
- No audiometry for workers in hearing protection.
- Entering a confined space with no permit or rescue plan.
- Trenching over 1.5m without shoring, benching or battering.
- Relying on BYDA plans without physically locating the services.
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