Invisible Danger: Red Cross Guide to CO Poisoning Care for AFA + EMR

Carbon monoxide (CO) is a silent killer. As an Advanced First Aider or Emergency Medical Responder (EMR), you're often the first healthcare contact a patient receives. Early recognition and prompt intervention in CO poisoning are crucial and can save lives—especially in settings where access to definitive care may be delayed.

This blog outlines the causes, signs and symptoms, pathophysiology, field assessment, and pre-hospital care strategies relevant to both Advanced First Aiders and EMRs.

What Is Carbon Monoxide?

Carbon monoxide is a colorless, odorless, tasteless gas produced by the incomplete combustion of carbon-based fuels, such as:

• Gasoline

• Natural gas

• Wood

• Coal

• Propane

It is often found in:

• Malfunctioning furnaces and heaters

• Gas-powered generators

• Indoor barbecuing or grilling

• Exhaust from vehicles in enclosed spaces

• Fires (house, structure, or wildland)

Because CO is undetectable without special equipment, individuals can be poisoned without any obvious warning signs.

Why Is It Dangerous?

CO binds to hemoglobin in red blood cells with 200 to 250 times greater affinity than oxygen, forming carboxyhemoglobin (COHb). This reduces the amount of oxygen that can be transported through the bloodstream and delivered to vital organs. As a result, even small exposures can lead to significant tissue hypoxia, especially in high-demand organs like the brain and heart.

Common Risk Scenarios for First Responders

You may encounter CO poisoning in any of the following situations:

• Residential emergencies involving fuel-burning appliances

• People found unconscious in a running vehicle (especially in enclosed garages)

• Victims rescued from structure fires or enclosed-space fires

• Use of charcoal grills or fuel heaters indoors

• Power outages leading to indoor generator use

Your scene awareness and understanding of environmental risks are essential in raising suspicion early.

Signs and Symptoms of CO Poisoning

Mild to Moderate Exposure

• Headache (often described as dull or pressure-like)

• Dizziness or lightheadedness

• Nausea and vomiting

• Fatigue or weakness

• Confusion or difficulty concentrating

• Shortness of breath with minimal exertion

Severe Exposure

• Altered level of consciousness or unresponsiveness

• Chest pain (especially in individuals with cardiac history)

• Tachycardia, hypotension

• Seizures

• Loss of coordination or balance

• Respiratory distress

• Coma or death

Children, elderly individuals, and pregnant patients are particularly vulnerable, and may deteriorate more quickly.

What About Pulse Oximeter (SpO₂) Readings?

This is a critical point for both EMRs and Advanced First Aiders:

Pulse oximeters are unreliable in carbon monoxide poisoning.

Why?

Pulse oximeters measure the percentage of hemoglobin saturated with something, but they cannot distinguish between:

• Oxyhemoglobin (HbO₂): hemoglobin bound with oxygen

• Carboxyhemoglobin (COHb): hemoglobin bound with carbon monoxide

Since COHb absorbs light in a similar way to HbO₂, the device will often display a falsely normal or high oxygen saturation (SpO₂), even if the patient is severely hypoxic.

Example:

A patient may have:

• A pulse oximeter reading of 98–100%

• But a COHb level of 30–40%, meaning oxygen delivery is critically impaired

Key Takeaway

Do not rely on SpO₂ readings in suspected carbon monoxide poisoning.

Instead:

• Focus on the scene context and presenting symptoms

• Administer high-flow oxygen regardless of oximeter reading

• Prioritize transport to definitive medical care

Pre-Hospital Management

Your early actions can dramatically improve outcomes. Here's what to do:

1. Ensure Scene Safety

Before entering a potentially contaminated area, ensure it is safe. Never enter confined spaces without proper PPE and backup support.

2. Remove the Patient from Exposure

Move the patient to fresh air immediately, but only if it is safe to do so.

3. Administer High-Flow Oxygen

• Use a non-rebreather mask at 15 L/min

• Oxygen accelerates the dissociation of carbon monoxide from hemoglobin:

  • Room air: COHb half-life ~5 hours

  • 100% oxygen: COHb half-life ~1.5 hours

  • Hyperbaric oxygen: COHb half-life ~30 minutes

4. Monitor Vital Signs

• Expect signs of hypoxia, even with normal SpO₂

• Monitor for respiratory distress, altered LOC, or shock

5. Rapid Transport

Any symptomatic patient requires prompt transfer to advanced medical care, especially if:

• They have altered mental status

• Are pregnant

• Exhibit neurological or cardiac symptoms

• Have been exposed for a prolonged period

Notify receiving EMS crews or hospitals of the potential CO exposure.

Special Considerations

Pregnant Patients

Fetal hemoglobin binds CO more readily than adult hemoglobin. CO exposure poses serious risks to the fetus, even if the mother appears only mildly symptomatic.

Pediatric Patients

Children may develop symptoms more quickly due to higher metabolic rates and smaller reserves.

Multiple Casualties

If several people in the same environment report similar symptoms (e.g., headache, dizziness), strongly suspect environmental CO exposure. Treat all individuals as potentially poisoned, even if some are asymptomatic.

Field Clues for CO Exposure

Use this quick field checklist:

• Is there a fuel-burning device involved?

• Are multiple people feeling sick in the same location?

• Do symptoms improve once outdoors?

• Is there poor ventilation or signs of combustion indoors?

• Does the patient seem "too sick" for their SpO₂ reading?

If yes to any of the above: suspect carbon monoxide poisoning and treat accordingly.

Quick Reference Table: SpO₂ in CO Poisoning

FactorNormal PatientCO Poisoning PatientPulse Oximeter (SpO₂)97–100%97–100% (falsely normal)Actual Oxygen DeliveryAdequateCritically impairedAppropriate ActionMonitorHigh-flow O₂ + transport

Prevention and Education

As a first responder, you also play a vital role in prevention. Encourage the public to:

• Install and maintain carbon monoxide detectors

• Keep fuel-burning appliances properly ventilated

• Never use outdoor cooking equipment indoors

• Avoid idling vehicles in enclosed spaces

• Seek medical attention after any CO alarm activation, especially with symptoms

  Carbon monoxide poisoning is a critical medical emergency that demands rapid recognition and decisive care. Both Advanced First Aiders and Emergency Medical Responders must understand that a normal SpO₂ reading doesn’t rule out danger. Situational awareness, oxygen administration, and timely transport are your most effective tools in the field.

  At our training center, we specialize in Advanced First Aid and EMR education, equipping students with the real-world skills needed to respond confidently to medical emergencies—including CO poisoning. If you're interested in becoming a firefighter or pursuing a career in emergency services, our programs are a strong first step.

  Many of our instructors are experienced paramedics and active-duty firefighters, bringing first-hand insights from the front lines directly into the classroom. You'll learn from professionals who live what they teach—preparing you not only to pass your course but to thrive in high-stakes environments.

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Understanding Hypoxia: A Firefighters guide

What is Hypoxia?

Hypoxia is a condition where there is a decrease in the amount of oxygen reaching the body's tissues.

a small medical device that is used to measure oxygen saturation levels in the blood. The device features a digital display screen and clips onto a person's finger. The screen displays a 98% SPO2 reading.

Causes of Hypoxia

Hypoxia can be caused by a variety of factors, including pulmonary disorders, cardiovascular disease, trauma, carbon monoxide poisoning, and drug overdose. Given the frequency of these causes in their work, firefighters must be prepared to recognize and manage hypoxia in emergency situations.

Overall, understanding the potential causes of hypoxia and being prepared to manage this potentially life-threatening condition is critical for firefighters and other first responders.

1. Respiratory emergencies:

   Conditions such as asthma, chronic obstructive pulmonary disease (COPD), and pneumonia can impair the lungs' ability to transfer oxygen to the blood, leading to hypoxia.

   Individuals with respiratory conditions may experience shortness of breath, rapid breathing, and wheezing, which can indicate a lack of oxygen in the body. These symptoms can worsen during periods of physical exertion, stress, or exposure to environmental triggers such as allergens or pollutants.

2. Cardiac emergencies:

   Cardiac emergencies are another potential cause of hypoxia in the prehospital setting. Conditions such as heart failure, heart attack, and pulmonary embolism can reduce blood flow to the body's tissues, leading to hypoxia.

   When the heart is unable to pump blood effectively, the body may not receive sufficient oxygen, resulting in hypoxia. Individuals with cardiac emergencies may experience symptoms such as chest pain, shortness of breath, and rapid or irregular heartbeat, which can indicate a lack of oxygen to the tissues.

3. Trauma:

   When an individual experiences severe trauma, such as from a motor vehicle accident or a fall, they may sustain injuries that impede their ability to breathe and deliver oxygen to their tissues.

   Injuries such as broken ribs or a collapsed lung can interfere with the normal mechanics of breathing, preventing sufficient oxygen intake. Additionally, traumatic injuries can cause significant bleeding, reducing the body's ability to transport oxygen to the tissues. In some cases, trauma can also lead to shock, which can result in decreased oxygen delivery to the tissues.

4. Carbon monoxide poisoning:

   When individuals inhale smoke from a fire, they may be exposed to high levels of carbon monoxide, a poisonous gas that can cause hypoxia by binding to the hemoglobin in the blood, reducing the amount of oxygen that can be carried to the body's tissues.

   A complication with carbon monoxide poisoning is that it can lead to a false readings when using an SpO2 monitor. This is because carbon monoxide can bind to hemoglobin in a similar way to oxygen, which can cause the SpO2 monitor to read a normal oxygen saturation level, such as 99%. However, even if the SpO2 reading appears normal, the individual may still be experiencing hypoxia due to carbon monoxide poisoning.

   Therefore, it's important to always administer high-flow oxygen to any fire patient, including those who have potentially been exposed to carbon monoxide. Providing high-flow oxygen can help to displace carbon monoxide from hemoglobin and increase the amount of oxygen available to the body's tissues.

5. Drug overdose:

   Many drugs, particularly opioids and sedatives, can cause respiratory depression, which means that an individual's breathing rate is reduced and they may not receive enough oxygen.

Symptoms of Hypoxia

The symptoms of hypoxia can vary depending on the severity of the condition and the underlying cause. Some common symptoms of hypoxia include shortness of breath, rapid or shallow laboured breathing, cyanosis (bluish tint to the skin), confusion or disorientation, headache, fatigue, nausea, rapid heartbeat, and dizziness or lightheadedness.

How to Check for Hypoxia Using an SpO2 Monitor

As an advanced first aider who is allowed to treat with oxygen, it's important to understand how to check for hypoxia using an SpO2 monitor. An SpO2 monitor measures the oxygen saturation in the blood, which can help determine if an individual is experiencing hypoxia.

To use an SpO2 monitor, follow these steps:

1. Turn on the monitor and place the sensor on the individual's fingertip.

2. Wait for the monitor to display the oxygen saturation percentage.

3. Take note of the percentage and compare it to normal levels.

What Percentage of Oxygen on the Monitor Indicates Different Severities of Hypoxia?

Normal oxygen saturation levels are typically between 95-100%. If the oxygen saturation level is below 95%, it may indicate hypoxia. The severity of hypoxia can be determined by the following percentage ranges:

1. Mild hypoxia: Oxygen saturation level between 90-94%.

2. Moderate hypoxia: Oxygen saturation level between 80-89%.

3. Severe hypoxia: Oxygen saturation level below 80%.

It's important to note that an SpO2 monitor is not a definitive diagnosis of hypoxia and should be used in conjunction with other symptoms and clinical assessments.

Treatment of Hypoxia

As an advanced first aider who is allowed to treat with oxygen, your first step in treating hypoxia is to administer high flow O2 via NRB (Non Rebreather) or BVM (Bag Valve Mask).

Administering supplemental oxygen is a key treatment measure for hypoxia, but it's also important to address the underlying condition that is causing the hypoxia. This may involve working closely with other healthcare providers, such as respiratory therapists or emergency medical services personnel, to provide comprehensive care.

Overall, as an advanced firefighter, being familiar with the causes, symptoms, treatment, and prevention of hypoxia can help you provide effective care and support to individuals who are experiencing this potentially life-threatening condition.