Three people with symptoms of carbon monoxide poisoning have been treated in hospital in Cornwall.
A fire crew was sent to a house in St Mabyn on Friday night following the activation of a carbon monoxide detector.
Two firefighters wearing breathing apparatus used gas detectors to measure carbon monoxide levels.
It is thought fumes from a wood burning stove caused higher than normal levels of the odourless gas.
The condition of the three casualties is not known.
About 4,000 people a year are diagnosed with CO poisoning in England and Wales, while accidental exposure to the gas is responsible for about 50 deaths a year.
Symptoms of CO poisoning include a headache, nausea, dizziness, vomiting and confusion.