Every second home is without a carbon monoxide (CO) detector, putting the lives of the occupants at risk of death from the gas.
In Ireland, about 40 people die from accidental CO poisoning each year, according to HSE figures.
Although four in 10 people are aware of the risk of CO poisoning, only 43pc have alarms installed in their homes, according to a survey commissioned by PhoneWatch.
It also found that 13pc of people were unaware of the causes of CO poisoning.
This is in spite of the gas being able to kill in just three minutes.
"Carbon monoxide is a highly dangerous and poisonous gas, you cannot see it or smell it which is why it is known as the 'silent killer'," said Managing Director of PhoneWatch, Eoin Dunne.
"It can often go undetected, leaving its victims disorientated, tired, nauseous and unconscious. In some cases it can prove fatal," he said.
CO can occur when any fossil fuel is burned - including oil, gas, peat, turf, wood and wood pellets, petrol, diesel and coal.
Although having an alarm can help households detect the gas, Mr Dunne said sometimes "they can be of limited effect".
"Generally people can be overcome by carbon monoxide fumes very quickly so are unable to sound the alarm to call the fire services," he said.
To deal with this, Mr Dunne said that people should be on alert for faulty household appliances. This can reduce the risk of CO. Warning signs include staining, sooting or discolouring around appliances which burn slowly.
The gas can also be indicated by a yellow or orange flame where one is normally blue, condensation or dampness on walls and windows, or a strange smell when an appliance is in use. For this reason, the regular maintenance and inspection of fuel-burning appliances is a must, according to PhoneWatch.
The figures come as part of Carbon Monoxide Awareness Week, which runs all this week.
The annual campaign was this year launched by Minister for Communications, Energy and Natural Resources Alex White.
"Carbon Monoxide Awareness Week addresses the regrettable fact that, notwithstanding previous safety campaigns, we continue to see terrible tragedies as a result of carbon monoxide poisoning," Minister White said.
"It is officially autumn now, and people will be switching on boilers that haven't operated for six months, lighting fires and closing windows - all things which potentially increase risk.
"This colourless and odourless gas is highly dangerous and I would urge people to take the simple preventative actions and install an audible alarm so they can rest assured knowing that they and their families are protected," he said.
Research released at the launch revealed that one in five people consider carbon monoxide as the most important safety risk in the home, second to fire.
Networks Safety Manager with Gas Networks Ireland Owen Wilson advises that people avoid "dangerous myths" surrounding the source of carbon monoxide.
"One of our core messages is that all fuels can cause carbon monoxide when burned, from any kid of appliance," he said.
"Symptoms of carbon monoxide poisoning are very similar symptoms to the flu, like headaches, chest pains, diarrhoea.
"It can be difficult for doctors to diagnose as symptoms can fade away, so if you think you have poisoning, go to the doctor immediately.
"Pets can also be affected by it," he added.