“The whole family’s had headaches, feel sick and dizzy at home — even the dog seems off — but we’re fine when we’re out”

CARBON MONOXIDE (CO) POISONING is recognised by non-specific FLU-LIKE symptoms — headache, nausea, dizziness, fatigue, sometimes confusion — affecting MULTIPLE PEOPLE and PETS in the SAME HOME, WORSE at home (mornings/heating on) and IMPROVING when AWAY; CO is the "great mimic", commonly misdiagnosed as a viral illness, migraine or food poisoning, so the household + pet + home-related + improves-away pattern is the crucial clue. Ask about the combustion source (gas boiler/fire/cooker, solid-fuel stove, blocked/faulty flue, poor ventilation, unserviced appliance) and a CO alarm. The immediate action is an EMERGENCY: get everyone (and pets) OUT into fresh air, turn off the appliance if safe, ventilate, don’t stay inside, and call the National Gas Emergency Service (0800 111 999) and 999/urgent assessment — CO can rapidly cause loss of consciousness and death, particularly overnight. Arrange urgent assessment: treatment is high-flow 100% OXYGEN (speeds CO elimination), a raised carboxyhaemoglobin level supports exposure (but it falls once away from the source and faster on oxygen, so a normal level taken late does not exclude it, and smokers have higher baseline levels), and hyperbaric oxygen decisions for severe cases (neuro signs, LOC, pregnancy, cardiac involvement) follow NPIS/TOXBASE advice. Critically, pulse OXIMETRY reads FALSELY NORMAL because it cannot distinguish carboxyhaemoglobin — a normal sats reading is misleadingly reassuring. Advise prevention: CO alarms, servicing by a registered (Gas Safe) engineer, ventilation, and no unsuitable appliances (BBQs/generators) indoors; landlords must arrange annual gas safety checks and CO alarms; and review for delayed neurological effects. The skill is recognising the pattern, immediate emergency advice, assessment without false reassurance from oximetry, and prevention — not labelling it viral.