Confined Space Entry on a Boiler Drum
An insulator crew is assigned to install 50 mm mineral wool and wire mesh inside a 2.4 m diameter boiler drum during a maintenance shutdown. The only access is a 450 mm manway. A portable blower is running, but the supervisor calls it “optional.” Before entry, a gas monitor reads 19.2% oxygen and 15 ppm carbon monoxide; the previous shift used solvent-based adhesive inside the drum. The outside ambient temperature is 36°C and the drum interior feels hotter. After about 20 minutes inside, a worker reports headache, nausea, and dizziness. The crew has a signed confined-space permit, but no attendant is stationed at the manway and the communication radio is shared with another work group. Two workers are already inside; one is wearing a half-mask respirator, but the other has only safety glasses. The supervisor wants the job finished before the evening shift.
1. What immediate actions should you take when the worker reports symptoms, and why?
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- Stop the work and evacuate the drum. Symptoms plus 19.2% oxygen are already outside common confined-space acceptance criteria (typically 19.5–23.5% oxygen). The CO reading and solvent adhesive use make the atmosphere suspect, and a permit is not valid when conditions change.
- Account for every worker and move them to fresh air. Provide first aid, cool the worker, and arrange medical evaluation for headache, nausea, and dizziness. Heat stress and possible CO or solvent exposure must be assessed together.
- Do not re-enter until the space is ventilated and re-tested. Use a calibrated direct-reading monitor and test before entry and continuously during occupancy. Confirm oxygen, CO, and solvent vapours are within applicable occupational exposure limits.
- Station a trained attendant at the manway with reliable communication and a rescue plan. The shared radio is not adequate for a confined-space entry.
- Notify the supervisor and safety representative, document the event, and reissue the permit only after controls are in place. The reasoning is that the original permit no longer reflects the actual hazard.
2. Using the hierarchy of controls, what changes would you make before re-entry?
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- Elimination/substitution: Remove the solvent-based adhesive from the confined space. Use a water-based or low-emission adhesive, or prefabricate as much insulation as possible outside the drum.
- Engineering controls: Increase forced ventilation with the blower positioned to supply clean air and exhaust contaminated air. Add cooling or work-rest cycles for the 36°C conditions. Use continuous gas monitoring with alarms.
- Administrative controls: Assign a dedicated attendant, establish a rescue plan, limit entry time, rotate workers, and train the crew on the revised permit. Confirm communication by radio or rope signal.
- PPE: Use respiratory protection only as a supplement, not as a substitute for ventilation. Select PPE based on the measured contaminants and heat stress.
Verify the controls by pre-entry testing, continuous monitoring, attendant observation, and stop-work triggers. The reasoning is that PPE alone would not correct oxygen deficiency or heat stress.
3. The supervisor insists the job must finish and says the monitor is too sensitive. What do you do?
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Refuse the unsafe entry and keep the crew out. Workers have the right and duty to refuse work they reasonably believe is unsafe. Do not alter, bypass, or ignore the monitor; ask for calibration records and a second calibrated instrument if the reading is disputed. Document the readings, symptoms, missing attendant, and supervisor’s direction. Report the matter to the joint health and safety committee or the jurisdictional OHS authority as required. The reasoning is legal and ethical: a confined space can become immediately dangerous to life or health, and production pressure does not make an invalid permit valid.