Two people from Lanivet were taken to hospital last night with suspected carbon monoxide poisoning.
Firefighters were called to the property in Truro Road after an alarm was triggered.
A spokesman for the service said; "Firefighters wearing breathing apparatus entered the property with a gas monitor to confirm the presence of carbon monoxide.
"An ambulance crew attended to care for two occupants showing symptoms of carbon monoxide poisoning. They were conveyed to hospital to be checked over.
"Ash that had been removed from the grate of a log burner and stored inside was identified as the source of the carbon monoxide.
"The ash was taken outside and the property fully ventilated before further readings were taken with the gas monitor to confirm the presence of carbon monoxide had been removed.
"This incident highlights that ash from a wood/log burner or open fire, even if it appears cold, should be disposed of with great care.
"In addition to the risk of fire, there is real danger that it will give off carbon monoxide, so never store it in a confined space."