Just a random question How would you control the amount of a

Solution

In a automatic life jacket like this, controlling pressure manually is not possible. The jacket is pressurised upon activation to the design pressure it was made for.

Automatic lifejackets activate when detecting water. Upon detection of water, a firing mechanism will activate and pierce a CO2 cylinder. The air coming out of the cylinder will inflate the bladder of the lifejacket and create buoyancy. Buoyancy is created by any material that is lighter than water. Manual-only lifejackets are activated by the user by pulling on a toggle or handle. By pulling on the toggle or handle a lever system gets released which will pierce the CO2 cylinder.

Lifejackets detect water depending on the type of operating/inflation mechanism the manufacturer of the lifejacket has chosen. Most lifejackets use CO2 cylinders as CO2 has proven to be adequate because of its properties of being non-toxic, non-inflammable, and because it can be stored in small disposable cylinders.

The life jacket in picture uses Halkey Roberts Automatic system. It activates when a salt bobbin gets in contact with
water. When the bobbin is in contact with water, it dissolves, allowing a spring to be released which pushes a plunger forward, in turn forcing a cutter into the CO2 cylinder. The cutter allows the CO2 to travel through the CO2 gas hole in the inflator head and inflate the lifejacket. The Automatic system is backed up by a manual override, which allows the user to pull the toggle and inflate the lifejacket. All lifejackets also have a third oral inflation tube.