Booth Airflow Failure Before a 2K Clearcoat
At a two-bay workshop in Tema, the downdraft spray booth's airflow gauge reads 0.20 m/s at the filter face; the booth manual specifies 0.35 m/s minimum, and the final filter was changed eight months ago. The painter has been assigned a 2K polyurethane clearcoat job on a customer's SUV, due for collection at 16:00. The hardener contains an isocyanate (HDI-based) and the SDS says respiratory sensitisation is possible. The only respirator in the shop is a half-mask with A1P2 combination filters, stored in an open cabinet, and one strap is cracked. The workshop supervisor says: 'Open the booth doors, switch on the fans, and spray - we cannot miss the deadline.' The painter has mild asthma and has already coughed after mixing the clearcoat. Two other workers are sanding nearby without extraction. A replacement final filter is in the store, but the fan belt is also loose and slipping.
1. Decide whether the clearcoat may be sprayed today. Identify the uncontrolled exposures and apply the hierarchy of control.
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Do not start spraying. The booth is below its minimum face velocity (0.20 vs 0.35 m/s), so aerosol and vapour will escape into the workshop; opening the doors reduces containment further. The painter's asthma and cough after mixing are signs of exposure, and isocyanate sensitisation can be permanent. A half-mask A1P2 with a cracked strap cannot be relied on: the face seal is unverified, and spray application of 2K isocyanate coatings normally requires air-fed respiratory protection, fit testing and health surveillance. Apply the hierarchy: engineering controls first - fit the new final filter, tension or replace the fan belt, verify airflow with a calibrated instrument, and repair the sanding extraction; administrative controls - reschedule the job and restrict booth access; PPE last. Substitution to an isocyanate-free product is not a like-for-like option for this clearcoat. Tag the booth out of service and report the defect.
2. The supervisor insists that you proceed. How should you respond, and what records should be created?
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Refuse in a calm, specific way: 'I cannot spray until the gauge reads at least 0.35 m/s; the fan belt is slipping and the filter is loaded.' Put the refusal and the reason in writing to the supervisor and owner, and ask for the booth to be tagged out. Record the date and time, gauge reading, filter change date, belt condition, respirator inspection, names of people present, the instruction given and the corrective action agreed. Photograph the gauge and the booth log. If the workshop has a hazard report form, use it; if not, a notebook entry sent by message is still evidence. Do not sign the job card or spray a test panel 'just to check'. The aim is to get the engineering fault fixed, not to win an argument. If pressure continues, escalate to the owner or safety committee.
3. A colleague does a short test spray and 20 minutes later complains of chest tightness and wheeze. What immediate actions should be taken?
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Stop the test spray, switch off the gun, and move the colleague to fresh air away from the booth; do not let them drive or stay alone. Sit them upright, loosen tight clothing, and call emergency medical help, stating possible isocyanate exposure. If they have a prescribed reliever inhaler, help them use it; do not give medication yourself. Keep the SDS and the product label ready for the medical team, and note the time exposure began. Report it as an incident, preserve the booth readings, and arrange medical follow-up. Chest tightness or wheeze after isocyanate exposure can be early sensitisation or asthma, so a return to spraying without medical clearance is unsafe. The booth stays closed until airflow and RPE are corrected.