A. 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).
B. Do not release mylar (foil) balloons outdoors. Power failures can result if these balloons become entangled in electric lines.
C. Popped latex balloons present a choking hazard for small children. Do not leave small children unaccompanied with latex balloons.