I have been using something that is better and easier and lasts longer than a typical balloon for my receivers. No chemicals to add and it's easy to put on and remove, no residue. It's self bonding water and air tight. It's chemical and UV resistant also. Temperature range is -60°F to 365°F. It's easy to apply and easy to remove.

It's tape by 3M called Professional All Weather Electrical Tape. Model 2575-Black. Best thing also it's like $3.00!

Try it.