Fume Extraction Failure on a Confined Fillet Weld
You are MIG welding 6 mm mild steel fillet joints inside a 2.4 m x 1.8 m x 2.1 m steel tank that has one 600 mm access opening. The portable fume extraction unit's flow indicator sits at the low edge of its green band. After 40 minutes your workmate reports a metallic taste, mild headache and dizziness. The tank has residual solvent smell from a previous coating. The supervisor says the job must finish today and suggests opening the access hatch wider and continuing. Your welding helmet lens is fogging, and the extraction hose lies on the floor beside you.
1. What should you do in the next five minutes, and why does the supervisor's suggestion not resolve the hazard?
Read the worked answer
Stop welding and withdraw from the tank. A metallic taste, headache and dizziness after 40 minutes in a confined space are consistent with exposure to welding fume and possibly solvent vapour, and symptoms are a trigger to leave, not to push on. Widening the hatch improves general ventilation but does not control the fume plume at the arc, and the extraction unit is already reading at the bottom of its acceptable band, so its capture is marginal. The hose on the floor is also likely kinked or drawing contaminated air. The solvent smell raises a second hazard: heat and UV from the arc can degrade residual coatings into additional irritant or toxic products.
The correct sequence is: stop work, exit, report to the supervisor and record the symptoms; have the space assessed and the extraction unit inspected (filter condition, hose routing, flow); confirm the atmosphere is safe before re-entry; and only restart with effective at-source extraction and a documented rescue/communication plan. Finishing today is not a reason to accept a known exposure.
2. The extraction unit is later found to have a blocked filter. Explain how you would verify the controls are adequate before resuming, and what records you would expect.
Read the worked answer
Replace or clean the filter, then verify performance rather than assuming it. Check the flow indicator reads mid-band or higher with the hose positioned to capture the plume at the arc, not lying on the floor. Inspect the hose for kinks, splits and correct placement. Confirm the tank has been purged and tested for flammable and toxic atmospheres if solvent residues remain, and that the coating has been removed or the space declared safe. Confirm the welder is not relying on the extraction alone: respiratory protection appropriate to the task, and a second person outside the space with a means of communication and rescue.
Records should include the pre-entry assessment, atmospheric test results, the equipment inspection and filter change, the reason for the stoppage and the corrective action, and the worker's symptom report. These records show the hazard was identified and controlled, and they support any follow-up health monitoring.