We have been Using Fox 40 products for 8 years at Footsteps of Discovery, this is the smallest of the three types of whistle that our instructors use at 110 decibels plus it packs a punch for it’s size. This is ideal for attaching to other items like a key fob.
The Fox 40 Micro are a 3 chamber pealess design and they are very loud for their size, it would be advisable not to use in a confined space. The Micro are also S.O.L.A.S. (safety of life at sea) approved.