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How Do Life Jackets Work?

Mark Armstrong
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Life jackets can be an important life saving device and can be an essential accessory when you’re on the water. But how exactly do they work?

To help you understand a little more about how life jackets can help you to stay afloat, we’ve put together a quick guide on what they do and how they work.

How Do Life Jackets Work?Pin


A lot of Personal Flotation Devices (PFDs) tend to be made with foam, which can provide buoyancy in the water. These foam filled life jackets can be easy to use and maintain, as they don’t require inflation. However, if you’re not used to them, they can feel bulky compared to inflatable life jackets.

Foam filled life vests can be used for a variety of water activities and will often be the most common type of life jacket given to you if you rent a kayak or paddle board, for example.

These life jackets tend to be worn as a vest over your clothing and are usually secured around your waist.

How do life jackets work?

They are an effective buoyancy aid that is worn either around the waist or as a vest. A life jacket can help to keep you afloat in the event that you end up in the water. It works because it weighs less than the water, creating lift and providing you with buoyancy while you’re wearing it.


Inflatable life jackets can be a suitable option if you’re paddle boarding, as these can often give you a little more freedom of movement than a standard foam filled PFD.

Inflatable life jackets can be less bulky than standard life jackets because they inflate either manually or automatically when you hit the water. This can make them more comfortable to wear for activities where you might want to be able to move with less restrictions.

​Video: Life Jackets and Inflatable Life Jackets

Inflatable life jackets can also come in different styles to standard foam filled ones, such as in the form of a waistpack, which is a PFD worn like a belt, meaning your arms and shoulders are free, for example, for paddling.

These belt-style PFDs usually require you to loop a section over your head after it’s inflated, so that your head can stay above the water. This means that a waistpack life vest may not be suitable if you end up in the water with no ability to do this, for example in the event that you lose consciousness.

​How Do Life Jackets Float?


Life jackets float because they are buoyant. Many standard life jackets are made using foam, which has air trapped inside the fibers. This air helps to minimize the density of the life jacket, which means it will be more buoyant when it’s in the water.

If you’ve ever studied physics, you’ll probably know a little bit about density and buoyancy. If something has a lower density than water, then it will likely float. You might have seen this with oil floating on water, as oil is lower in density than water.

​Inflatable Life Vests

Inflatable life jackets will usually have a cartridge containing air, or carbon dioxide. Some PFDs will require manual inflation and others will automatically inflate when you hit the water.

With a manual inflatable, you will usually have to pull a cord to trigger the air supply to the life jacket. A life jacket with automatic inflation is designed to trigger the air supply when it’s submerged in water.

A manual inflatable life jacket might be more suitable than an automatic one for certain watersports where you may frequently come into contact with the water. With an automatic one you may find that it could inflate when you don’t really need it, such as from splashes or if you want to jump off your kayak or paddle board for a swim.

Inflatable life jackets, both manual and automatic, will tend to have the option of increasing the amount of air in the vest by using a mouthpiece. This is similar to the life vests you find on aircraft, which allow you to top up your life vest by blowing into the attached tube.

Foam-Filled Life Vests

Many life jackets are made using foam materials because of the high levels of buoyancy. These types of PFDs help to keep you afloat in the water without requiring an air source to be triggered. This means they can be easy to use and will provide buoyancy straight away, as the material itself is designed to float.

Foam materials tend to hold trapped air, which helps to increase buoyancy by reducing the density of the material. Foam can also be found in other products because of its buoyancy, for example in the hulls of kayaks.

> Guide to kayak bulkheads

​Final Words

Life jackets should be a vital part of your equipment when it comes to water sports, as they can be effective life saving devices when worn correctly.

Whether you choose a manual or automatic inflatable life jacket or a standard foam one, these PFDs can help to give you the added buoyancy you need to stay afloat in the water.

Let us know what you think by leaving us a comment and help keep your fellow water enthusiasts safe by sharing this guide with them.

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