Helium is used in observation of ballons because it is?

Helium is used in balloons because it is light and non-combustible. Helium is a gas that is much lighter than air, which means that when it is filled inside a balloon, the balloon rises up into the air. This makes it ideal for use in observation balloons, as it allows the balloons to float and stay aloft for extended periods of time. In addition, helium is non-combustible, which means that it does not catch fire or ignite easily. This makes it a safe choice for use in balloons, as it eliminates the risk of fire or explosion that can be caused by other, more flammable gases. Overall, the combination of being light and non-combustible makes helium a popular choice for use in balloons, as it provides a safe and effective way to keep the balloons aloft.