Asking whether it is safe to sleep with the heating on is quite a big question. A lot of it is going to be based around the type of heating that you have. Although, generally speaking, it is probably not a good idea to have the heating turned on when you are asleep because even central heating could be bad for our health.
Space heaters are a huge 'no' when it comes to falling asleep. In fact, some experts claim that you shouldn't have a space heater in your home at all. Yes. They can save money, but they are among the most dangerous heaters that you can own. It has been estimated that just under 80% of all fatal house fires are actually caused by space heaters.
Why are they so dangerous? Well, because they can get incredibly hot. This can result in items left close by being warmed up to the point that they catch on fire. If you are awake, then you will probably see this happen. However, if you are asleep, there is no chance you will see that a fire has started until it is far too late.
A lot of homes in Australia still have gas heaters installed. You should barely have one of these turned on at the best of times. Gas heaters are incredibly unsafe. In fact, if you haven't had a heater service carried out on your gas heater in the past two years, then don't switch it on at all.
Why are they so unsafe? Because gas heaters that haven't had a heater service can let out carbon monoxide. This is a gas that 'silently kills'. While you could feasibly spot the symptoms of carbon monoxide poisoning when you are awake, there is zero chance you will be able to spot them when you are asleep. Faulty gas heaters take the lives of several Australians each year. They shouldn't be in the home.
If you do have a gas heater in your home or any sort of heater that works by 'combusting' material (e.g. briquette heaters) then do talk to a heater technician. Ask them to look over it to see whether it is safe before you switch it on.
In theory, central heating is among the safest heating there is. However, in many cases, the central heating will still run on gas. This means that you will need to call in a heater repair company every couple of years to look at the heater. If you spot any small issues with the heater, then you will also want to have it repaired quickly. Central heating also causes deaths in the home from carbon monoxide poisoning.
Even if we put all the potential fire risk and carbon monoxide poisoning to one side, most doctors recommend that you do not fall asleep with a heater on anyway. They claim that it will mess with your sleeping patterns. If you get too hot at night, you will not fall into a deep sleep. This will guarantee you won't be waking up feeling refreshed.
In an ideal world, you will turn the heating on in a room for an hour or two before you sleep. Then you turn it off just before you climb into bed. This is the safest route to go down, and it ensures the highest amount of safety.