Television watchdogs have banned a commercial for the Sun newspaper which shows a man inhaling helium from a party balloon.
Viewers were concerned that children could be asphyxiated
The commercial, which was promoting a two-for-one offer at Alton Towers theme park, prompted complaints from several viewers who said children might do themselves harm by copying it.
After inhaling the helium, the man spoke in a high-pitched squeaky voice.
Seventeen viewers, some of whom worked with helium, complained to the Independent Television Commission (ITC), saying there were potentially serious dangers to anyone - particularly children - who inhaled the gas, which could lead to asphyxiation.
The viewers pointed out that equipment used to fill helium balloons carries health warnings which make it clear that helium can cause asphyxiation and should not be inhaled.
The advertising agency which made the commercial, TBWA, argued that asphyxiation only occurred when the brain was starved of oxygen, and since the helium used to fill party balloons contained oxygen, the danger was negligible.
But the regulator ruled that inhaling helium was potentially dangerous and the commercial should not be shown again.
Although there have been no known deaths in the UK from helium inhalation, there is some evidence from around the world that it can be fatal.
The inhalation of helium cuts off a person's supply of oxygen and can cause dizziness, unconsciousness and even death.
Doctors in Australia - where one girl reportedly turned blue and fainted after inhaling the entire contents of a helium-filled balloon - have said there can be a particular problem when people have drunk a lot of alcohol and their system is already contending with an outside influence.