St Emlyn’s Lesson Plans

Carbon monoxide: recognise the exposure, protect the household

Assess possible carbon monoxide exposure, interpret a later blood result and plan care that includes the safety of the home.

Early-career Emergency Medicine · 45-minute session

For learners

Before: Allow about 18 minutes in total.

When we meet: We will discuss a family exposed at home and a patient who remains confused after oxygen treatment.

After: choose a point to follow up in practice

For facilitators

Send: the learner preparation link before teaching.

Bring: Whiteboard, official algorithm and a blank exposure timeline. No actual gas equipment, patient images or laboratory access is required.

Run: 45-minute session plan · 30-minute option

Before the session

If you are attending this session, complete the core preparation below before you come. Allow about 18 minutes in total.

Core preparation

UKHSA: Carbon monoxide diagnostic algorithm · About 5 minutes

Read the exposure questions and actions in the UKHSA diagnostic algorithm, including questions about other people at the address.

https://www.gov.uk/government/publications/carbon-monoxide-co-algorithm-to-diagnose-poisoning

UKHSA: Carbon monoxide incident management · About 10 minutes

Read the clinical first-aid section, including immediate treatment and when detailed TOXBASE or NPIS advice is needed.

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1077807/UKHSA-incident-management-carbon-monoxide.pdf

Think about (allow 3 minutes): How would oxygen treatment and time away from the source affect your interpretation of a COHb result?

Picture the scene

Five family members arrive after an engineer condemns their gas fire. They feel well now and ask for a blood test to prove they can go home.

By the end of the session

Elicit an exposure history that includes other people, symptom timing and the environment.
Interpret oxygen saturation and carboxyhaemoglobin in relation to oxygen treatment and elapsed time.
Plan immediate care, specialist discussion and safe discharge without returning people to an unsafe source.

After the session

Find the actual local route for making an unsafe home safe outside office hours, and identify who records that action in the patient’s plan.

Facilitator guide

Send learners the preparation link several days before teaching. Allow about 18 minutes in total.

Before learners arrive

Confirm local access to TOXBASE and the current NPIS contact route without sharing account details. Ask how the ED communicates with gas/fire services and public health when more people may be at risk.
Use the two written cases to draw exposure, leaving the building, oxygen and sampling on a timeline. Mark times that have not been supplied as questions to ask, rather than inventing a COHb curve. Check local discharge information and arrangements for persistent neurological symptoms.

Equipment: Whiteboard, official algorithm and a blank exposure timeline. No actual gas equipment, patient images or laboratory access is required.

Setup: Work in trios: patient/family spokesperson, clinician and observer. The observer listens for unanswered environmental questions and for assumptions made from test results.

If the preparation has not been completed

Replace the five-minute opening with an exposure timeline. Ask pairs to place leaving the building, oxygen and blood sampling in order, then use the UKHSA algorithm to identify what a later result may miss. Keep the algorithm open during the cases. In the 30-minute plan, use five minutes here and reduce the family case from 10 to eight minutes.

Suggested session plan

0–5 min — Exposure before investigations. Read the family hook and ask what the department needs to know before offering reassurance.
5–18 min — Household case. Map affected people and practical source-control actions; allow a learner to challenge the discharge plan.
18–33 min — Timeline and severe features. Reveal the second case progressively and rehearse a focused specialist referral.
33–40 min — Discharge explanation. Ask pairs to explain a low later result in plain language, then check for unintended reassurance.
40–45 min — Consolidate. Close with one clinical and one environmental action that must have an owner.

Start the discussion

Read the opening scenario together. Give everyone a moment to think, then ask what concerns them and what they need to know next.

Cases and discussion

Use these cases, or invite an anonymised case from the group that addresses the same questions.

The family and the condemned fire

Two adults and three children have spent the evening in a room with a faulty gas fire. One adult had a headache and a child vomited earlier, but both feel better outside. They want to return for the children’s school things.

Add this information as the discussion develops:

Ask who needs assessment and which missing history matters before ordering a family panel of tests.
One adult is pregnant. An older relative may still be at the address.
The family’s blood samples are taken several hours after leaving. The results are not markedly raised.

Ask the group:

What does the pattern across household members suggest?
Who else may be exposed, and who can make the building safe?
How would pregnancy affect your threshold for specialist advice?
What would you say when the family interprets the blood results as permission to go home?

Discussion notes

Points to draw out:

A compatible exposure and symptom pattern matter even when people improve outside. Assess each person; children and pregnancy need appropriate specialist pathways.
Ordinary pulse oximetry can be misleading in CO poisoning. Obtain appropriate co-oximetry, but interpret the result with elapsed time, oxygen and smoking history; a low later value cannot erase the earlier exposure.
A discharge plan must address the source and other potentially exposed people. Do not advise re-entry until the relevant emergency/gas safety service has made the environment safe.

Common misconceptions:

Equating “well now” with no clinically relevant exposure.
Treating several family members as a single clinical assessment.

For a more experienced group: Add a landlord who says the boiler was recently serviced. Practise explaining why this does not override an actual exposure concern.

Improving after oxygen, but still confused

A 25-year-old used a camping stove indoors. A friend found them drowsy. After ambulance oxygen they feel better, but the friend says their memory is unusual. A later COHb result is 4%.

Add this information as the discussion develops:

Ask learners to state what the result does and does not establish.
Reveal chest discomfort and a new ECG abnormality.
Ask the group to make a concise call to the senior clinician and poisons service, with the exposure and oxygen timeline included.

Ask the group:

Which alternative or additional causes of reduced consciousness need assessment?
Which features make simple discharge inappropriate despite the low result?
What information would make a specialist consultation more useful?
How would you explain the possibility of delayed problems and follow-up needs?

Discussion notes

Points to draw out:

Provide high-concentration oxygen and supportive ABCDE care while assessing neurological and cardiac involvement. UKHSA directs clinicians to TOXBASE/NPIS for detailed management.
Severe neurological features, cardiac injury, acidosis, pregnancy or uncertainty require senior and specialist discussion. Hyperbaric oxygen decisions are case- and service-dependent; do not promise benefit or use a single COHb cut-off as the whole referral rule.
Check intentional exposure sensitively. If relevant, physical treatment and mental-health/safety assessment must both be addressed.

Common misconceptions:

Using the post-oxygen COHb result to dismiss the friend’s history.
Focusing on hyperbaric treatment while delaying ordinary oxygen and stabilisation.

For a more experienced group: Ask an experienced group to explain the risks of interhospital transfer alongside the possible benefit of specialist therapy.

Important clinical points

Do not delay oxygen while waiting for a COHb result.
Do not return a household to the suspected source because blood tests are reassuring.

Closing the session

Use these questions to check what the group will take away. Go back over any clinical points that remain unclear.

Why can a normal saturation be misleading?
How would two hours of oxygen change your interpretation?
Who will confirm that the address is safe?

Key teaching points:

Ask about the exposure, symptoms in other people and what happened after leaving the building.
Interpret COHb alongside the time of exposure, oxygen treatment and blood sampling.
Improvement in symptoms does not mean the source is safe to return to.

Before leaving, ask each person to choose one action from After the session and say when they will try it. They complete that follow-up in practice, with supervision where needed.

Adapting the discussion

Uncertainty and local practice

Hyperbaric treatment and follow-up decisions need current specialist advice. Discuss the exposure, symptoms, treatment timeline and practical transfer risks with the appropriate service.

If the discussion drifts

What does this result tell you at this time, and what important question has it left unanswered?

For a more experienced group

Discuss a fire exposure with possible additional toxicants, or the competing priorities of caring for several exposed people simultaneously.

A 30-minute version

30-minute option: opening 3, family 10, symptomatic case 12, discharge and closing 5. Omit transfer debate.

Evidence and guidance

UKHSA: Carbon monoxide incident management — Initial clinical care and incident management; use TOXBASE/NPIS for detailed advice about an individual exposure.https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1077807/UKHSA-incident-management-carbon-monoxide.pdf
UKHSA: Carbon monoxide diagnostic algorithm — Exposure questions, recognition and actions when carbon monoxide poisoning is suspected.https://www.gov.uk/government/publications/carbon-monoxide-co-algorithm-to-diagnose-poisoning