AP Diluent First Stage

AP Diluent First Stage

Replacement part for all AP rebreathers

The AP Diving FS101 (diluent), FS101A (oxygen), and FS101A/G (oxygen with Euro Thread) 1^st stages are designed specifically for the AP Inspiration range of closed-circuit rebreathers. They are state-of-the-art 1^st stages utilising a diaphragm-based balanced design, a unique port layout scheme and a 'stream-through' design to combat freezing. 

They are CE approved and designed to easily pass the EN250:2000 norm for performance and anti-freezing. 

These stages are manufactured specifically for the AP Inspiration range of closed-circuit rebreathers. This has resulted in the following special features:

• 4 LP ports and 2 HP pressure ports that are placed in a non-standard position to accommodate perfect hose routing within the casing of the Inspiration rebreathers, both on the diluent-side (FS101) and oxygen-side (FS101A) of the rebreather.
• An anti-freeze approach utilising large stream-through ports on the diaphragm side of the 1^st stage, allowing the ambient water to transfer its above-zero warmth to the 1^st stage. 
• The choice of materials used in manufacture, support this heat transfer.
• A very stable medium pressure delivery, even at depth. This is accomplished by using the above described heat transfer approach instead of the more popular “sealing” approach. Sealed 1^st stages (where the diaphragm is kept isolated from the environment by an oil- or air-filled space and a second, flexible membrane) typically creep up in medium pressure at depth, as such bringing with them the danger of a solenoid not operating due to the medium pressure being too high. 

The design and gas delivery capacity of this 1^st stage is such that it will easily accommodate open-circuit usage at depth as well. When used in a rebreather, this means this 1^st stage can also fulfil an “open circuit bail-out” role when needed at any depth the Inspiration rebreathers are rated for.

PLEASE NOTE: The RB17 14 Bar Pressure Relief Valve is not included with a replacement First Stage and needs to be purchased separately. 

The RB17 is an over-pressure valve that screws into a spare low pressure port on your first stage. If the high pressure seat fails on your first stage, the RB17 will vent when the interstage pressure reaches 14 bar and so prevents high pressure gas delivery to your second stage.