Deck Restoration, Sanding, and Oiling

Yes. The International Agency for Research on Cancer (IARC) classifies hardwood dust as Group 1 — carcinogenic to humans. The specific cancer type is adenocarcinoma of the nasal cavities and paranasal sinuses, with a long latency period (typically 5–30+ years between exposure and diagnosis). The Australian Workplace Exposure Standard is 1 mg/m³ (8-hour TWA) for hardwood dust and 5 mg/m³ for softwood dust. Common Australian decking hardwoods (spotted gum, merbau, blackbutt, ironbark, jarrah) all generate carcinogenic dust when sanded. Power sanding without adequate dust extraction can easily exceed the WES within minutes. P2 respirators, dust extraction on all sanders, and HEPA vacuum cleanup are essential controls.

CCA (Copper Chrome Arsenate) treated timber contains arsenic (up to 37 % of treatment), chromium (up to 45 %), and copper (up to 25 %). Sanding CCA-treated decking generates toxic dust containing these compounds. Arsenic is associated with increased lung cancer risk; hexavalent chromium is associated with nasal cancer. Required controls: P2 respirator minimum (consider P3 for heavy sanding); HEPA-filtered dust extraction on all sanders; dust-sealed goggles; long sleeves and trousers; wash all exposed skin thoroughly after work; launder work clothing separately. NEVER burn CCA dust or offcuts (releases arsenic fumes). Dispose of all CCA sanding dust at a licensed waste facility — not in general waste or green waste. Contact your local council or EPA for specific disposal requirements.

Oil-soaked rags (particularly those soaked with products containing linseed oil, boiled linseed oil, or tung oil) undergo spontaneous combustion. These "drying oils" undergo exothermic oxidation as they cure — they generate heat as a chemical byproduct of the drying process. When oil-soaked rags are bunched together, piled up, or placed in an enclosed space, they act as thermal insulators that trap this heat. The temperature can rise to ignition point (~120 °C) without any external flame or spark. Fires from spontaneous combustion have destroyed homes and buildings, and typically occur hours after work is completed — often overnight. Prevention: ALL oil-soaked rags must be placed IMMEDIATELY into a metal container filled with water and sealed with an airtight metal lid. Alternatively, spread rags flat on a non-combustible surface outdoors to dry completely. Never leave oil-soaked rags in piles, plastic bags, rubbish bins, vehicles, or enclosed spaces.

Using too much pressure damages timber — it raises grain, splinters the surface, and can require significantly more sanding to repair. Recommended pressures: softwood (cedar, pine): 500–600 PSI maximum; general hardwood (merbau, spotted gum, blackbutt): 1,000–1,200 PSI; composite decking: under 3,100 PSI with fan-tip nozzle minimum 200 mm (8 inches) distance. General rule: start at the lowest effective pressure and increase gradually. Always use a fan-tip nozzle (15° or 25°) — never a pencil jet (0°) on timber. Maintain at least 300 mm (12 inches) distance between nozzle and surface. Work with the grain. After washing, allow 24–48 hours of drying time before sanding with electrical equipment.

For sanding: P2 respirator (minimum, fit-tested — hardwood dust is IARC Group 1 carcinogenic), dust-sealed safety glasses or goggles, hearing protection (Class 3+ earmuffs — sanders produce 80–95 dB), anti-vibration gloves, long sleeves and trousers (minimises skin contact with carcinogenic dust), safety boots. For CCA-treated timber: upgrade to P3 respirator consideration for heavy sanding. For oiling/staining: chemical-resistant nitrile gloves, safety glasses, P2 respirator for oil-based products, half-face respirator with organic vapour + particulate cartridge (A1P2) for two-pack polyurethane or spray application. For pressure washing pre-clean: face shield, waterproof boots, waterproof clothing, hearing protection.

Isocyanates are chemical compounds found in two-pack polyurethane coatings and some premium deck finishes. They are one of the most significant occupational respiratory sensitisers — meaning they can permanently alter your airways so that even tiny future exposures trigger severe asthma-like reactions. Sensitisation can occur from a single high exposure or from prolonged low-level exposure. Once sensitised, there is no cure — the affected worker may be permanently unable to work around isocyanates. The Australian WES is 0.02 mg/m³ (8-hour TWA) and 0.07 mg/m³ (short-term 15-minute). Symptoms include nose, throat, and eye irritation, coughing, wheezing, shortness of breath, and chest tightness. If using two-pack polyurethane products: brush/roller application with half-face respirator (A1P2 cartridge) minimum; spray application requires full-face supplied-air respirator. The safest approach is to substitute single-pack oil-based or water-based deck coatings, which do not contain isocyanates.