They tested a 17-year old heater which had not been properly maintained and found that it produced lethal amounts of carbon monoxide in less than ten minutes. When gas doesn't burn properly it produces excess carbon monoxide, which is poisonous. You can't see, smell or taste carbon monoxide and it can kill, without warning, in a matter of hours. Where these symptoms affect more than one person in the home, or where they improve when away from home but recur upon return, carbon monoxide poisoning may be the reason. If this cracks, pieces of cement fall out and leave gaps in the seal.
Gas then burns behind the panel, instead of in front of it.
The vast majority of mobile gas fires are perfectly safe and incidents of gas poisoning are rare but we are taking the recent deaths very seriously and fully support HSE's action to publicise the potential dangers. Help to make sure that there are no more unnecessary deaths.