The Public Health Agency is urging people to be vigilant for the signs and symptoms of carbon monoxide poisoning.
It follows the deaths of two teenagers in Castlerock on Tuesday due to a suspected carbon monoxide leak.
Aaron Davidson and Neil McFerran, both 18, and from Newtownabbey died in a holiday apartment. A friend survived.
The PHA has recommended a series of actions to minimise the risk of carbon monoxide poisoning.
• installing an audible carbon monoxide alarm that meets British or European standards. These cost about £20 and can be purchased from large DIY stores and food retail stores.
• sweep chimneys and flues every year if you use solid fuel;
• if you are in rented accommodation ask your landlord to provide you with an up-to-date gas safety record. This is a requirement by law and is particularly important for students renting houses and flats;
• keep flues, air vents and grilles clear and ensure rooms are well ventilated.
Initial investigations suggest the carbon monoxide source in the Castlerock case was a liquefied petroleum gas-fuelled appliance.
Dr Anne Wilson, consultant in health protection at the PHA said: "The signs and symptoms of carbon monoxide poisoning are often mistaken for other illnesses, such as food poisoning or flu.
"The symptoms can be similar to flu but without a raised temperature."
The gas is produced when fossil fuels such as gas, coal, oil, wood, petrol and paraffin burn without enough oxygen.
It is a colourless, tasteless, odourless gas that is non-irritating.
Symptoms include headaches, nausea, exhaustion; drowsiness; dizziness and palpitations.
"Anyone who suspects they may be suffering from carbon monoxide poisoning should immediately turn off all appliances, go outside and seek medical help from a qualified healthcare professional.
"Appliances should not be used again until they have been serviced by a registered engineer," Ms Wilson said.