Regardless of the style, a BCD has five features which are necessary for scuba diving. We will take you through these features, explaining their purpose and why you need to look for these when buying your own BCD. Like anything, there are additional features available for your BCD but this depends on personal preference and different models from manufacturers.
As explained in the purpose section, BCD's must allow you to have positive buoyancy to float comfortably at the surface. In order to do this, you must make sure the volume of air the BCD holds is enough to keep not only you, but all your other equipment afloat as well. You can control your buoyancy using weights also, but if you are particularly big or small, ensure you have a suitable BCD to cater for this.
Inflation/ Deflation Mechanism
Secondly, your BCD must have large diameter inflation and deflation mechanism to supple and release air quickly and easily. In most cases it is hose, but on some designs, it is a left hand toggle named an i3. It is recommended for beginners to use a traditional inflation and deflation hose as this is what you will learn with and be more comfortable using in the water. However, i3s relieve you of the space that the tube takes up and are preferred by some more experienced divers. Again, it is down to personal preference so try both styles on and see which one is more comfortable for you. Don't be tempted to go for something stylish if it does not perform properly; safety is the most important factor of any dive equipment.
Low-Pressure Inflation System
Every BCD should have a system for inflating it with air directly from your cylinder. As covered in the Inflation/Deflation Mechanism, this can sometimes be a toggle names an i3 which you press one way to inflate and the other to deflate. The more common, which your see on the end of the inflation hose, is a handheld device with two separate buttons, one at the side and one at the top. One will be for inflating you BCD (usually the bright coloured one), and the other, you guessed it, is used for deflation, usually found in the top of the device. This design is pretty universal across a wide range of manufacturers for ease of use, double check your individual BCD manual for any alternative instructions.
Overpressure Relief Valve
Your BCD must have a valve or other similar mechanism which will automatically release air if your BCD becomes overfilled with air. You don't want your BCD to rupture due to overfilling which will damage it beyond use meaning you will have to replace a vital and costly bit of equipment.
Because air expands during ascent, over inflation can occur even without you manually filling your BCD with cylinder air, which is why it is important for even the most careful and experiences divers to have a relief valve on their BCD.
It goes without saying that you shout be comfortable on every dive; in order to fit a BCD comfortably, it will come with adjustable strap which you can alter to fit you suitably.
Pockets and D-Rings
You might want to think about additional features for you BCD such as pockets and D- rings. Whilst these aren't important for the correct functioning of your BCD they are very useful depending on the kind of diving you will be doing. Often D-rings come already bent to flare out making attaching clips and accessories much easier than with flat D-rings which lie against the BCD. In tropical waters, only one or two small pockets will suffice useful for carrying things like your Fish ID slate. For UK and cold water diving, you will probably need to carry more equipment such as a DSMB and reel or spare mask making more attachments or bigger pockets preferable.
This is the part of the waist band which wraps around your waist, and is usually secured with Velcro before a secure clip is fasted on top of it. They are not mandatory but come as standard with most BCD models you see today as they provide more comfort and prevent other straps and equipment from rubbing or digging in your suit.
Quick dump valves can vary depending on different models and they are not a mandatory feature of BCDs. They are usually located in the shoulder straps and allow you to conveniently release air from your BCD without holding the inflation system up. These are especially useful on restricted dives such as wreck dives, as it means you do not have to adjust your swimming position to alter your buoyancy.
Integrated weight systems
Another common feature of modern BCDs is the integrated weight system which offers an alternative to wearing a separate weight belt around your waist. Weights, along with a BCD, are the two main methods of controlling your buoyancy in the water. It is crucial that these integrated systems can be quickly released to drop weight fast in case of emergency which is why many now come with a pull tog system; however other methods such as clips and Velcro are available. Some people might wish to use this integrated weight system in addition to a weight belt if they require a big pull to help them descend in the water. The suitable weight needed for negative buoyancy varies and is specific to the individual. If you do require a heavier BCD, led shot weight pouches are available which fit conveniently into your BCD weight pockets.
Other desirable features include whistles utility rings, hose retainers. There are also special BCDs designed for females and children, find out more about them in selecting the right BCD for you.
Integrated Weights System