Carbon monoxide (CO) poisoning often feels like the flu or food poisoning at first, but it can quickly become life-threatening. If you suspect it, leave the building immediately and call emergency services or local poison control.

Carbon monoxide symptoms (Quick Scoop)

CO is called the “silent killer” because it has no smell, color, or taste.

Early and mild symptoms

These are the ones that most often get mistaken for “just a bug”:

  • Headache (often dull, persistent).
  • Dizziness or feeling light‑headed.
  • Feeling sick or vomiting.
  • Tiredness, fatigue, or weakness you can’t explain.
  • Confusion, “brain fog,” difficulty concentrating.
  • Flu‑like feelings but usually without a fever.
  • Irritability or subtle mood/behavior changes.

A classic red flag: several people (or pets) in the same space all feeling unwell at the same time, especially when they’re at home and feel better when they go outside.

More serious / high level exposure

As levels or exposure time increase, symptoms can escalate quickly:

  • Shortness of breath, breathing fast or feeling you “can’t catch your breath.”
  • Chest pain or fast heartbeat.
  • Blurred or poor vision.
  • Loss of coordination (stumbling, clumsiness, trouble walking straight).
  • Strong confusion, agitation, personality changes, or acting drunk.
  • Muscle weakness or loss of limb function.
  • Seizures, loss of muscle control, or collapse.
  • Loss of consciousness, coma, or death.

On some health sites, “face turning hot and red (flushing)” is mentioned, but this is not always obvious on darker skin tones.

Long‑term or repeated low‑level exposure

Being exposed to lower levels for weeks or months can cause more subtle but serious problems:

  • Persistent headaches and fatigue.
  • Ongoing dizziness and nausea.
  • Difficulty thinking clearly, memory problems, and poor concentration.
  • Mood and personality changes, including irritability, depression, or impulsive decisions.

These can easily be misdiagnosed as stress, anxiety, or a viral illness if CO is not considered.

What forums and real people talk about

In forum and Reddit‑style discussions, people often describe:

  • Worrying about vague dizziness, headaches, and anxiety and wondering if it’s “just in their head” or CO.
  • Being told “don’t ignore it; CO can kill you fast, call emergency services and let them decide.”
  • Relief after getting a proper CO detector and seeing normal readings, or finding out a faulty appliance was the cause.

A common theme: people feel silly for overreacting, but others stress that it’s better to overreact with CO than to dismiss it.

“Make a big deal out of it, that stuff will kill you, and it will do it quick.” – typical advice‑style comment in online threads.

When to treat it as an emergency

Call emergency services or go to the ER immediately if:

  • You have sudden headache, dizziness, nausea, weakness, or confusion while near fuel‑burning appliances (heaters, boilers, generators, fireplaces, car in garage).
  • Several people or pets in the same building are sick with similar symptoms.
  • Your CO alarm is going off, even if you feel “mostly okay.”

Basic steps recommended by public health and emergency guidance:

  1. Leave the building or car right away; go outside into fresh air.
  1. Call emergency services (or local gas/emergency line) from outside or from a neighbor’s place.
  1. Do not go back inside until professionals say it is safe.

Example: Someone wakes up with a pounding headache and nausea every morning in winter, which eases when they go to work. The boiler or heater is later found to be faulty and leaking CO into the bedroom.

Simple HTML table of key symptoms

html

<table>
  <thead>
    <tr>
      <th>Exposure level</th>
      <th>Common symptoms</th>
      <th>Notes</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>Low / early</td>
      <td>Headache, dizziness, nausea, fatigue, mild confusion, flu-like symptoms without fever[web:1][web:3][web:5][web:7][web:9]</td>
      <td>Often mistaken for viral illness or food poisoning[web:1][web:3][web:9]</td>
    </tr>
    <tr>
      <td>Moderate</td>
      <td>Worsening headache, vomiting, shortness of breath, chest pain, blurred vision, poor coordination, behavior changes[web:1][web:3][web:5][web:7][web:9]</td>
      <td>Symptoms may improve when leaving the building and return when you go back in[web:7][web:9]</td>
    </tr>
    <tr>
      <td>Severe</td>
      <td>Seizures, loss of muscle control, collapse, loss of consciousness, coma, death[web:1][web:3][web:9][web:10]</td>
      <td>Medical emergency needing urgent oxygen treatment[web:1][web:5][web:9]</td>
    </tr>
    <tr>
      <td>Long-term low-level</td>
      <td>Persistent headaches, fatigue, mood changes, memory or thinking problems[web:3][web:9]</td>
      <td>Can be misdiagnosed without considering CO exposure[web:3][web:9]</td>
    </tr>
  </tbody>
</table>

“Latest news” and ongoing context

Recent public health and research updates still highlight that:

  • Household CO exposure is strongly linked to faulty gas appliances, solid fuel stoves, and poor ventilation worldwide.
  • Authorities continue winter safety campaigns reminding people to service heaters and use certified CO alarms.

Researchers are actively modeling how CO builds up in homes to better guide prevention and alarm standards.

If you’re worried right now

  • If you have symptoms plus any possible CO source (gas heater, generator, car in garage, blocked flue, etc.), get into fresh air and call urgent medical or local emergency services.
  • If it’s not an emergency but you’re concerned, arrange:
    • Check/servicing for boilers, heaters, and chimneys by qualified professionals.
* Installation of certified CO alarms on each level of your home and near sleeping areas.

You should also contact a doctor or nurse line if you’ve had ongoing unexplained headaches, nausea, or fatigue at home, especially if others in the home feel the same.

Bottom note: Information gathered from public forums or data available on the internet and portrayed here.