A woman's chance purchase of a home safety device saved her life and also that of her husband.

For the carbon monoxide detector began ringing within ten minutes of Glenis and Keith Allan switching it on at their home in Harewood Road, Keighley.

The level of the lethal gas was so high the couple were just hours away from death.

The couple had started to feel unwell over Christmas, but put it down to a bout of flu.

Both Glenis and Keith had been experiencing dizziness and headaches over the festive period.

But what they didn't realise was that their symptoms were being caused by a potentially lethal gas leak from the boiler in their council flat, which is fitted with a hot air heating system.

Glenis, 56, says: "For the past couple of weeks we had been feeling unwell with 'flu like symptoms.

"We don't spend that much time at home as we both work full time, but we were at home on Boxing Day and both felt really unwell.

"I went to bed in the afternoon and my husband fell asleep on the settee. At tea time my daughter Gill rang to invite us to her house for a family party, and although neither of us felt like going out we decided to go for a couple of hours. This no doubt saved our lives.

"On getting up the following day we both continued to feel unwell and I expressed the feeling that our heating system could be contributing to us both feeling unwell.

"I work at Argos in Keighley and when I found out that we sell carbon monoxide detectors I bought one, just out of curiosity.

"When we got home from work we turned on the heating and fitted the detector with batteries.

"Less than 10 minutes later the alarm started ringing and we couldn't reset it.

"I rang the gas board, who told us to turn off all the gas and to open all the doors and windows, and within 30 minutes a gas man had arrived and disconnected our heating system. We were told that the amount of fumes being admitted could have proved fatal within hours.

"Someone from Powerminster arrived the following day to check it out and found that the flue was so badly blocked the inside of the boiler was thick black. He said the detector had obviously saved our lives.

"The boiler was only serviced a month ago and I hate to think what would have happened if it had been our 80-year-old neighbour and not us."

CORGI, the national gas safety watchdog, says around 30 people in Britain die from the "silent killer" - carbon monoxide - each year.

The deadly gas is produced at dangerous levels when a gas appliance has been incorrectly installed or maintained, or when a flue or chimney has become blocked.

Signs that the gas is present include sooting or staining around the appliance, a yellow or orange lazy flame burning instead of a crisp blue one and excessive condensation in the room where the appliance is installed.

Symptoms of carbon monoxide poisoning are similar to those of a viral infection and include drowsiness, weakness, headaches, nausea and pains in the chest.

If anyone has these symptoms while using a gas appliance the unit should be turned off and checked by a CORGI registered installer. Those affected should also consult a doctor.

Chief executive of CORGI Bob Henry says: "Carbon monoxide is invisible, odourless and tasteless, and if left undetected can be deadly. Even exposure to relatively low levels of this highly poisonous gas can cause brain damage or death.

"To protect your family from the dangers of carbon monoxide ensure all gas appliances receive an annual safety check."

The watchdog also advises people never to DIY with gas and ensure that ventilation and flue terminals are kept clear.

For further details about CORGI registered installers call 01256 372300 or log onto the website www.corgi-gas.com.

A Bradford council housing spokesman says: "Our contractors visited the flat on December 28 and found that the boiler needed some new parts. These have since been installed and all repairs were completed on December 30."