National Poisons Information Service

A service commissioned by Public Health England




Members of the public

seeking specific

information on poisons

should contact:


In England and Wales:

NHS 111 - dial 111


In Scotland:

NHS 24 - dial 111


In N Ireland:

Contact your local GP or

pharmacist during

normal hours; click here

(www.gpoutofhours for GP

services Out-of-Hours.


In Republic of Ireland:

01 809 2166



professionals seeking

poisons information

should consult:

Carbon monoxide

Carbon monoxide (CO) exposure remains a common form of poisoning in the UK, however relatively little is known about its epidemiology. Since July 2015, NPIS has undertaken a project funded by the Gas Safety Trust to obtain more information, in particular confirmation of exposure, from healthcare professionals contacting the NPIS.

Data are collated from telephone enquiry data via the UK Poison Information Database and follow-up questionnaires posted directly to all enquirers. For healthcare professionals accessing TOXBASE, a questionnaire is either emailed or posted directly to the user or their head of department if contact details were not submitted at the time of viewing TOXBASE. Overall, in the period July 2015 to December 2017, data were collated and evaluated for 2,074 patient-related cases following exposure to carbon monoxide in the UK.


During the period January 2017 to December 2017, data were available for 835 patient-related exposures. Two hundred and twenty three (26.7%) were male, 250 (29.9%) were female. Gender was not specified for 362 (43.4%) patients. Exposures comprised 544 adults (≥13 yrs, 65.1%) and 144 children (≤12 yrs, 17.2%). Age was undetermined in 147 exposures (17.6%). Seventeen exposures involved pregnant women (2.0%).

Exposures in 808 patients (96.7%) were unintentional. Of these, activation of a CO alarm prompted the patients to seek medical attention in only 128 (15.8%) cases. Twenty seven patients (3.2%) were exposed due to deliberate self-harm.


When smoke/fire as the source of CO was excluded (n=90, 11.1%), the highest proportion of unintentional exposures were caused by domestic boiler issues (174, 24.2%), gas appliances (67, 9.3%), vehicle exhaust fumes (63, 8.8%) and domestic wood/coal fire burners (43, 6.0%). These CO exposures were most commonly of low severity (446, (62.1%) cases associated with no symptoms or mild symptoms only), with moderate severity recorded in 31 (4.3%) cases, severe symptoms in one (0.1%) case and death in two (0.3%) cases. Of the exposures in pregnant women, five were asymptomatic (PSS: None), 11 had symptoms of minor severity and one patient had symptoms of moderate severity.

Central nervous system symptoms were most prominent (250, 29.9%, patients presenting with one or more symptom), followed by effects on gastrointestinal system (108, 12.9%), then respiratory effects (44, 5.3%) and cardiovascular (41, 4.9%).

Blood carboxyhaemoglobin (COHb) concentrations were reported for 346 (41.4%) patients. The concentration was calculated from a blood test in 239 patients, a breath test in 18 and pulse oximeter in 20 patients. The test type was not reported for 39 patients.

A positive correlation was observed reported between symptom severity and blood COHb concentration.

The data presented here demonstrate the ability of the NPIS to collect valuable data on all aspects of CO poisoning from across the UK. With ongoing funding, the NPIS will continue to collect data to improve our understanding of the incidence and characteristics of CO poisoning in the UK.






Information from the NPIS Annual Report 2017/18.


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