The Fume Cloud in the Basement Plant Room
You are part of a two-person team doing fit-out in a basement plant room of a commercial building in Parramatta. The room is 6 m by 4 m with one doorway and no mechanical ventilation. You are welding steel brackets while your offsider grinds nearby. After 40 minutes your offsider complains of a headache, dizziness and a metallic taste, and says the air 'feels thick'. There is a portable extraction unit in the corridor, but it has no ducting attached and the filters were last changed eight months ago according to a tag. A single 1 kg dry powder extinguisher hangs by the door. The hot work permit on the wall is signed but lists a different room number. Your offsider wants to finish the last three brackets, about 20 minutes' work, before lunch.
1. What is happening, and what should you do immediately?
Read the worked answer
The symptoms - headache, dizziness, metallic taste, a sense of thick air in a confined, unventilated space - are consistent with exposure to welding fume and grinding dust, and possibly to oxygen displacement or build-up of carbon monoxide and metal-oxide particulates. This is a potential immediate risk to health, not something to 'finish before lunch'.
Immediate actions
- Stop work. Both processes stop; switch off the welder and grinder.
- Get out and get air. Move your offsider into the corridor or outside, sit them down, and keep them under observation. Do not let them return.
- Do not re-enter to finish the brackets. Three brackets are not worth an exposure incident.
- Escalate. Notify the supervisor, first aid, and if symptoms persist or worsen (confusion, breathlessness, chest pain) call 000. Record the time, symptoms and what was being done.
- Isolate. Lock out the plant, tag the room, and prevent others entering until it is assessed.
Why the existing controls failed
- The extraction unit is not connected and its filter tag shows it is overdue - it is not functioning as a control.
- The room has no mechanical ventilation and one doorway; natural dilution is inadequate for welding and grinding.
- The hot work permit is for a different room, so the task is being done outside its authorised scope and without the specified controls.
- One dry powder extinguisher is not a fume control; it addresses fire only.
What must be in place before restarting
- Ducted, functioning local exhaust ventilation at the arc and the grinding point, with current filter records.
- Supplementary general ventilation or forced-draft fans moving air through the room.
- Respiratory protection selected for welding fume (e.g. a P2/P3 half-face or PAPR) as a secondary control, fit-checked.
- A corrected hot work permit for this room, a fire watch, and a suitable extinguisher and fire blanket.
- Air monitoring if there is any doubt about exposure levels, and health monitoring considered for the workers involved.
2. Using the hierarchy of control, set out how you would control the fume hazard for the remaining work, and explain why PPE alone is not acceptable.
Read the worked answer
The hierarchy of control ranks controls from most to least effective, and the WHS Regulations require you to work down it, using PPE only when higher-order controls cannot reasonably eliminate or minimise the risk.
Applying the hierarchy to welding and grinding fume
- Eliminate: Can the brackets be prefabricated off site or bolted instead of welded? If so, the fume source disappears. This is the best option and should be considered first.
- Substitute: Use a lower-fume process or consumable, or a mechanical fixing instead of welding. Grinding could be replaced by cutting to size.
- Engineering controls: This is where most of the gain is here. Ducted on-torch local exhaust ventilation capturing fume at the source, plus forced ventilation to change the air in a 24 m³ room with one opening. Segregate hot work into a designated, ventilated area. Enclose the grinding with a shroud connected to extraction.
- Administrative controls: A valid hot work permit for this room, a fire watch, rotation to limit exposure time, housekeeping, training, signage, and air monitoring to verify the controls work. These depend on people behaving correctly, so they sit below engineering controls.
- PPE: Respiratory protection (P2/P3 or a powered air-purifying respirator), welding helmet, gloves, FR clothing and eye protection. PPE is the last line - it only protects the wearer, it fails if not fitted or worn, and it does nothing for anyone else in the room.
Why PPE alone is not acceptable
- It does not reduce the fume in the space; the offsider's symptoms show the room itself became hazardous.
- It relies on correct selection, fit, donning and maintenance every time, and on the wearer recognising when it has failed.
- It provides no protection to other trades who enter the room.
- Using PPE as the primary control for a known, controllable fume source is a failure to minimise risk so far as is reasonably practicable.
The right answer is to fix the ventilation and the permit, and use PPE as the backstop.