Video report by Kate Lewis
A mother that lost her son and grandparents to carbon monoxide poisoning has welcomed a change in the law in Wales.
Landlords must now fit working detectors in their rental properties.
Adele Forbes from Gilfach in Bargoed has been campaigning for nearly two decades, for more stringent rules on alarms in people's homes.
Her son McCauley, 5, and grandparents, Gloria, 69, and Patrick, 71, died in their home in October 2005 after a chimney flume in the house was blocked.
Now landlords in Wales must fit carbon monoxide detectors as well as fire alarms, otherwise their property will be deemed unfit for human habitation.
Known as the "silent killer", records show that between 20 - 60 people die each year from carbon monoxide poisoning and thousands more are treated in hospitals.
Carbon monoxide can be made by fires and appliances which burn gas, wood, oil or coal. It can kill people within minutes when it builds up indoors to deadly levels very quickly.
It can also be poisonous at low levels if people are subjected to it over time.
People often find themselves feeling better when they leave the indoor area where the heat source is based and then tend to feel worse when they return.
Symptoms of carbon monoxide poisoning include:
feeling sick or being sick
chest and muscle pain
shortness of breath
The symptoms may come and go. They may get worse when you spend time in an affected room or building and get better when you leave or go outside.
There are now concerns that safety corners will be cut with consumers tempted to keep energy costs down by using equipment like barbecues to cook indoors or to heat their homes.
There are also concerns that people will put off having appliances serviced if they cannot afford it.
Recalling when her family died, Adele told ITV News she hopes people will take notice and ensure they've got alarms fitted in their homes.
Her son McCauley went to stay with her grandparents on 25 October 2005. She had gone to pick him up the next day when she witnessed the worst had happened.
She said: "I entered the property and you could smell this strong sulphur smell, I know carbon monoxide hasn't got a smell, but it was the old coal boiler and you could just smell this strong sulphur-eggy smell.
"As we went in, my grandfather was on the kitchen floor and McCauley was upstairs in bed and so was my Nan."
Adele told ITV News when she realised they had died it was terrifying and she couldn't really process what was happening.
"It was three to four hours before the fire service confirmed that they were all deceased. That evening, it was something that happens to other people, not us."
"It's something you would read about in the Take a break magazine, somebody's sad story, but that sad story was then happening to us.
"I lost a massive part of my life that day."
Adele said she hadn't known much about carbon monoxide poisoning before, but when she thinks back her Nan had been ill with symptoms linked to the gas.
"I know that it's a build up over a period of months, which then took me back to thinking about the previous six months, my Nan was always unwell.
"My Nan spent a lot of time in the house, my grandfather was always in-and-out of the garden. She always felt sick. So when I used to go down and sit with my Nan for a few hours, I used to feel sick down their all the time and it was a running joke with my granddad saying there's something wrong with this house."
"When I'd go home after about an hour or so I'd feel okay, but now I know what it was and because my Nan was so ill all the time with her mental health, she was on a lot of medication and the doctor would always put it down to something like that."
A coroner's report showed the family would have died between 23:00 and 03:30 on the evening in October.
On that night the carbon monoxide produced in the home was so strong that it caused their death. Adele said she now hopes people will hear her story and take carbon monoxide very serious.
"If I can change people's perception or maybe just save one life by telling my story then in the end it's something good that has come out of something bad."
Adele has described her grandparents as being "absolutely fantastic, the most crazy, funny family you could ever wish for.
"They would do anything for anybody, a heart of gold."
She said McCauley "was funny, cheeky, very, very wicked...he was definitely one of a kind, he kept me on my toes."
Bleddyn Jones, the head of Community Safety for South Wales Fire and Rescue has joined calls for people to install carbon monoxide detectors in their homes and stressed the huge importance of them.
Top tips for staying safe from carbon monoxide
Install carbon monoxide alarms in all rooms with fuel-burning appliances, and rooms where people sleep.
Be prepared. Save the Gas Emergency Number into your phone: 0800 111 999 so you know who to call in a gas or carbon monoxide emergency.
Keep on top of regular maintenance. Ensure all gas and fuel-burning appliances are serviced every 12 months.
Never block vents or air bricks. Without fresh air, carbon monoxide can build up.
Turn on an extractor fan when cooking or open a window if you don't have one.
Make sure your chimneys are swept each year.
Test your carbon alarm regularly.
Teach others who live with you never to ignore the sound of the alarm - make sure they know the steps to take: 1. Turn off appliances if using them 2. Open nearby windows 3. Leave the property and call the Gas Emergency Service number on 0800 111 999.
Learn the symptoms of carbon monoxide poisoning so you can recognise potential exposure and act.