Firefighter with smoke exposure: interpreting carboxyhaemoglobin and return to work
A 31-year-old wholetime firefighter attends a large warehouse fire involving plastics and furniture. He wears breathing apparatus, but removes it during 'overhaul' and spends about 40 minutes in visible smoke. Four hours later he has headache, nausea and dizziness. Venous carboxyhaemoglobin is 12% in the emergency department. He smokes 15 cigarettes a day. He has no chest pain, ECG and troponin are normal, and peak expiratory flow is 90% of his personal best. He is keen to return to his next shift in 48 hours and asks whether he needs any further checks.
1. How would you interpret the carboxyhaemoglobin result and the exposure history?
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- A COHb of 12% is above the usual smoker baseline (roughly 5–10%, higher with heavy smoking), but the test was taken about 4 hours after exposure. CO half-life on room air is around 4 hours, so the peak level was substantially higher than 12%; the measured value cannot be used to estimate peak exposure directly.
- Smoking and occupational exposure are additive. You cannot apportion the result precisely, but the symptoms and the 40 minutes in smoke without breathing apparatus make a significant occupational CO exposure likely.
- CO is not the only relevant combustion product. Smoke from plastics and furniture may contain hydrogen cyanide, acrolein, irritant gases and fine particulates. Headache, nausea and dizziness are non-specific and do not exclude cyanide exposure.
- Delayed pulmonary oedema and irritant-induced airway injury can occur after smoke inhalation; he should be observed and reassessed rather than discharged immediately.
- Repeat COHb, document smoking status, examine the chest, and consider lactate and chest imaging if symptoms persist or worsen.
2. What advice would you give about fitness to return to his next shift in 48 hours?
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- He should not return to operational duty in 48 hours. He is still symptomatic and has had a significant smoke exposure with a raised COHb.
- Recommend rest from firefighting until he is asymptomatic, examination is normal, and COHb has fallen to a non-smoker-equivalent level (commonly <5%, or clearly back to his own baseline). Arrange review at 24–48 hours and again before return.
- At review, check for persistent cough, breathlessness, chest signs and peak flow; arrange spirometry if there are respiratory symptoms. Refer to a respiratory physician if symptoms persist beyond a few days.
- Advise him not to smoke in the immediate period, as this both delays CO elimination and confounds assessment.
- Record the event as an exposure incident and ensure the fire and rescue service reviews why breathing apparatus was removed during overhaul.
3. What organisational lessons and exposure controls would you recommend after this incident?
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- Overhaul is a recognised high-exposure phase: visible smoke and smouldering materials can generate CO and irritants even when flames are out. Breathing apparatus should be worn until the atmosphere is confirmed safe.
- Recommend atmospheric monitoring (CO and other gases) before and during overhaul, and a clear rule that BA is not removed in smoke.
- Review decontamination: removal of contaminated kit, washing, and personal hygiene before eating or drinking.
- Consider whether other crew members had symptoms; a short questionnaire and COHb screening may identify unrecognised overexposure.
- Feed back to the incident commander and health and safety team; record the incident and any RIDDOR-reportable overexposure. Include the case in training on smoke exposure and BA discipline.