From the Golden Retriever 'Care and Maintenance' manual -

10.3.4 (a) ii - Inflatable Toys.
When playing with your Golden Retriever, ensure all inflatable rubber chew toys use compressed air, nitrogen, xenon or methane. Do NOT use Helium (He), or the lycanthropic derivative Helium 5 (HeHeHeHeHe) with ANY chew toys, as this may cause your Golden Retriever to become lighter than air should the toy puncture and gas enter the respiratory system. Another side-effect may be a noticeable high-pitched barking noise due to the action of the gas on the dog's vocal cords. (See 'Chihuahua.')

16.2.3 (w) iv - Disclaimers (Inflatable Toys [Helium filled]).
In the event that your Golden Retriever ingests Helium gas, use a medium-speed projectile weapon (arrow, dart, shotgun) to puncture the dog, thus facilitating its return to earth. Please note--Golden Retriever breeders will accept no responsibility for damage caused by, or loss of, floating dogs for any reason.