Birthday Butterflies in Flight mylar balloon

SAFETY PRECAUTIONS
-Do not breathe helium from a balloon. Helium is not toxic nor flammable, but breathing it can result in asphyxiation (loss of consciousness due to insufficient oxygen).
-Do not release mylar (foil) balloons outdoors. Power failures can result if these balloons become entangled in electric lines.
FLOAT TIMES FOR MYLAR BALLOONS
In optimum environments, mylar (foil) balloons will remain full and taut for 3-5 days. They will continue to float for two weeks or longer. Air-conditioned air may cause these balloons to shrivel, but they will return to a normal state when exposed to warmer air.