The balloon will eventually pop, and you most likely can find its pieces at the coil if using AC, or smell rubber burning if using heater.
Yes, a balloon getting sucked into a return vent can potentially block the airflow and cause the AC system to work harder, leading to potential damage over time. It is advisable to have the balloon removed promptly to prevent any issues with the AC system.
Reverse the fan? Otherwise, need to know the what and where of the filter that was "sucked up."
You need a filter retainer
The filter might have been too strong for the gold fish to swim awa from, so it got sucked in
Try changing your fuel filter/lines. It could have had sucked something into the lines and cannot get any more fuel through.
Did you add more returns? If so there is your answer. When the return duct is sized properly, there is minimal negative static pressure or sucking.
The oxygen is taken out of the bottle so it gets sucked in.
None. Those engines draw so much air a filter would be sucked into the engine.
In the intake. You can spray it directly on the air filter and it will be sucked into the intake.
Air is pulled into the crankcase from the PCV (positive crankcase valve) the fresh air enters through this filter to keep dirt from being sucked into the crankcase. This filter is usually located inside the air filter housing.
Ripe fruits produce ethylene gas, which helps them ripen and soften. When this gas is captured in a sealed environment such as a balloon, it can inflate the balloon by increasing the pressure inside. Thus, a ripe fruit can indirectly help blow up a balloon by releasing ethylene gas.
Actually the filter on an automatic transmission is just a screen to keep the big chunks of metal from being sucked up into the pump. Most people replace them because they come with the kit of a seal and filter.