Carbon Monoxide Poisoning: What to Do and When to Seek Help

Carbon monoxide has no odor, color, or taste, so we rely on the combination of circumstances and symptoms. Suspect CO if headache, nausea, dizziness, weakness, drowsiness, confusion, chest pain, or shortness of breath occur in a room with a heating appliance/fireplace/water heater, near a running generator, or in a car garage. Symptoms often come and go and disappear outside. They can occur simultaneously in several people in the same apartment. "Cherry skin" is a late sign and almost always postmortem, so it should not be relied upon. [1]

If you suspect CO, don't rely on your sense of smell (there's no odor) and don't be reassured by the absence of smoke. The peak season is late fall and winter, when windows are closed and chimney draft is unstable. Symptoms develop more quickly and are more severe in children, pregnant women, the elderly, and those with heart or lung disease. [2]

Remember the key: location + time + symptom cluster. If everyone in the apartment with the water heater suddenly develops a headache, but the pain improves outside, this is practically a diagnostic pattern. In a high-rise building, pay attention to your neighbors: their complaints increase the likelihood of a common cause. [3]

Even low but prolonged CO concentrations are dangerous: memory delays, fatigue, anxiety, and sleep disturbances are possible—these manifest themselves days to weeks later. Therefore, "mild" symptoms should be taken seriously.

The "first 60-90 seconds" algorithm

1. Immediately leave the premises and take all people and animals to fresh air. Don't open windows "for ventilation" if this means staying inside—your job is to get out. If someone is unconscious, ensure your own safety first, then evacuate the victim. [5]
2. If you're outside, call an ambulance or gas company and report: "Suspected carbon monoxide poisoning, there are casualties." If you have a portable CO detector and it's activated, tell the operator the readings (this will be useful for the crew). [6]
3. Before paramedics arrive, administer oxygen if it's available (e.g., in sports clubs/industrial facilities): any mask with 100% oxygen accelerates the displacement of CO from hemoglobin. In normal air, the half-life of carboxyhemoglobin (COHb) is ~4-6 hours; with 100% O₂, it's reduced to ~60-90 minutes, and in a hyperbaric chamber, to 15-30 minutes. [7]
4. If the person is not breathing/unconscious, begin CPR using the standard algorithm until emergency medical personnel arrive. CPR often affects the heart and brain; early CPR is critical. [8]

First aid before and during transportation

In the fresh air, place the victim in a semi-sitting position, warm them, remove tight clothing, and reassure them—anxiety and hyperventilation can worsen symptoms. Monitor breathing: if vomiting occurs, turn the head to the side to prevent aspiration. Avoid alcohol and sedatives—they can mask the deterioration. [9]

If you have a portable pulse oximeter, remember: it cannot differentiate between oxyhemoglobin and carboxyhemoglobin and may "show normal" levels in cases of severe poisoning. Rely on clinical data and exposure history, not SpO₂. [10]

In an ambulance, the standard is 100% oxygen via a mask with a reservoir until hospitalization, monitoring, and blood sampling for COHb (co-oximetry). Indications for intubation are based on general criteria (depression of consciousness, respiratory failure, respiratory tract burns from a fire). [11]

If poisoning occurs during a fire, remember that cyanide poisoning is common: the clinical picture is more severe, and hypotension and lactic acidosis are possible. This is a separate hospital protocol; it is important to mention the fire to the emergency team. [12]

What will happen in the hospital and who needs a hyperbaric chamber?

In the emergency department, the diagnosis is confirmed based on COHb levels and clinical findings, 100% oxygen is continued, an ECG/cardiac markers, basic tests, and neurological status assessment are performed. The therapeutic goal with standard pressure is to maintain 100% oxygen until symptoms resolve and COHb levels drop to <10% (lower in pregnant women and those with heart disease). [13]

Hyperbaric oxygen therapy (HBO) is indicated in severe cases: loss of consciousness, neurological deficit, cardiac ischemia/arrhythmia, severe metabolic acidosis, COHb usually ≥25% in adults (the threshold is lower in comorbidities). For pregnant women, HBO is the preferred treatment even in moderate cases, because the fetus is vulnerable to hypoxia. The decision is made by a toxicologist/resuscitator. [14]

It's important to understand the role of HBO: it shortens the half-life of CO and can reduce the risk of late neurological complications in severely ill patients. It is recommended more aggressively during pregnancy. For fire inhalation, HBO is combined with treatment for possible cyanide poisoning. [15]

Even with low COHb, treatment is not stopped "at the drop of a hat" if symptoms persist: clinical signs are more important than the number. In elderly patients and patients with coronary artery disease, the threshold for inpatient observation is lower due to the risk of myocardial ischemia. [16]

What you absolutely must not do

Don't return to the premises "for a minute" to retrieve documents or a phone—this is a common cause of repeated injury and death. Wait for emergency services until they give permission. [17]

You can't "ventilate from the inside," much less turn on fans/exhaust fans, while remaining in the area—you're wasting time in a dangerous environment. Ventilation is the responsibility of specialists once the premises are deemed safe for entry. [18]

Don't rely on a standard pulse oximeter or "good" SpO₂ readings—they're a false sense of security. Also, don't take sleeping pills or alcohol "to fall asleep and make it go away"—there's a risk of unnoticeable worsening. [19]

If poisoning occurs at work, do not attempt to "turn on the ventilation and continue your shift" on your own. Isolation of the source, access to the area, and examination are the responsibility of occupational safety/emergency services. [20]

After discharge: how to recover and what to look out for

Even mild cases can cause delayed neurological symptoms, including memory and concentration impairment, depression/anxiety, sleep disturbances, and headaches. Tell your doctor if these symptoms appear within days to weeks of the event—they are not "imaginary," but a known consequence of CO.

During the first few weeks, avoid strenuous exercise and overheating, drink plenty of fluids, and get adequate sleep. If you experience cardiac symptoms (chest pain, arrhythmia), consult a cardiologist for a follow-up plan. [22]

Discuss with your doctor the timing of your return to work/exercise. In case of household poisoning, be sure to complete a technical inspection of the premises before returning to your home/office. In buildings with central heating, notify your property management company. [23]

For pregnant women, closer obstetric observation is recommended after exposure, even if the condition quickly returns to normal. [24]

Prevention: What really works

The most important thing is CO detectors: install them on every floor and near bedrooms, change the batteries regularly, and follow the manufacturer's instructions. A CO detector is not the same as a fire alarm; most smoke detectors do not detect CO. Have gas appliances, boilers, and chimneys serviced annually. [25]

Never use generators/grills/heaters indoors, in the garage, or near windows and vents. Do not leave a running car in a closed garage, even with the door open. Keep furnace, water heater, and dryer vents clear of snow. These simple measures prevent most tragedies. [26]