A total of 40 people have been taken to hospital with carbon monoxide poisoning in the past six weeks, the Dutch fire brigade said on Tuesday.

Carbon monoxide is spread by defect central heating boilers, poor ventilation and blocked-up chimneys.

‘It is not yet really cold but we have already had so many problems,’ spokesman Jet Vroege said. There have been 18 separate incidents involving what Vroege called the ‘silent killer’ in the past six weeks.

Last year, two people died and 114 people were hospitalised after carbon monoxide leaks, the fire brigade said.

The symptoms of carbon monoxide poisoning include sleepiness, headaches and nausea.