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Post Dive Procedures

  - unload scrubber , store in air tight container (Tupperware) and
wipe canister seals
  - Rinse hoses between dives on same day
  - Rinse unit after 1 day's use
  - Disinfect and dry hoses and unit after 5 day's use

Carbon Dioxide (CO2) Scrubber

Each exhalation consists of three components: reduced-oxygen content, carbon dioxide (CO2), and water vapor.  As will be discussed in the next section, we can increase the reduced-oxygen content gas with supply gas and rebreathe it with the appropriate level oxygen content.  However, before we can rebreathe the gas, we must remove the CO2.  Any failure in this respect could result in a potentially fatal CO2 build up, known as HYPERCAPNIA.
Fortunately, our exhalation contains water vapor and CO2, which combine to form Carbonic Acid.  Carbonic Acid is easily neutralized when it is exposed to a base substance such as 'Softnolime".  Therefore, a rebreather solves the CO2 build-up problem by directing exhaled gas through the loop to a CO2 scrubber, where it is neutralized.  The scrubbed exhalation gas travels through the loop toward the mouthpiece, where supply gas is introduced.  The method of supplying the fresh gas to the rebreather is another means of classifcation, and may be actively or passively accomplished.

As we know, our exhalation contains CO2, water vapor, and other gases.  When CO2 comes into contact with water vapor, it forms carbonic acid.

An Acid + a Base = Neutral

Thus, the easiest way to eliminate CO2 is to utilize its acidic chemical
properties.  By simply passing CO2 laden gas (acidic) through an alkali
(base), the CO2 is neutralized and removed through an exothermic reaction.
This heat producing reaction enables rebreather divers to breathe warm,
moist gas that enables them to stay warm and hydrated.
Generally speaking, there are two types of alkali to chose from, lithium
hydroxide or soda lime.  Lithium hydroxide is a very powerful alkali that is
also very lightweight.  These properties would seem to make it the perfect
choice for rebreathers.  Unfortunately, it has one major drawback; it will
KILL you if you flood the scrubber.  Therefore, lithium hydroxide should be
relegated to application in non-aqueous environments such as hospitals or
space.  Although not quite as powerful as lithium hydroxide, soda lime works
very well in rebreather applications.  In keeping with our principle that
simplicity is best, soda lime is a simple mixture of caustic soda (NaOH) and
lime (Ca (OH)).

The basic process of manufacturing soda lime is simple to understand.  The
process begins with a kiln fired to 1000 degrees Celsius used to drive CO2
off quarried chalk (calcium carbonate).  In doing so, calcium oxide is
formed.  The manufacturer then adds water to hydrate and reactivate the
calcium oxide, thus forming lime.

When choosing soda lime, granule size is important.  Soda lime granule size
is determined and referred to by the size of the mesh it can pass through.
Generally speaking, the two sizes are 4-8 mesh, or 8-12 mesh. The 4-8 mesh granules are passed through a mesh with openings between 2.5 and 5 mm. Therefore, they are larger than the 8-12 mesh, which must pass through
openings between 1 and 2.5 mm.  The smaller the granule, the more surface
area and absorption capacity you will have.  Unfortunately, with higher
absorption performance, comes higher breathing resistance, since the density
of the granules is greater with smaller granules.  Therefore, we recommend
using the 4-8-mesh size.

CO2 Absorbent Management

Packing Scrubber?
To pack the scrubber, flip the unit over. Unlatch the two latches on the
side of the unit and be careful as it is spring loaded. PLUG THE WATER TRAP TUBE. Next pour in the appropriate scrubber media. Replace the fine meshed screen and then the follower screen (heavy mesh), then the follower. Now replace the pring and the bottom unit and reattach the latches.. Your
scrubber is now packed and ready to dive. For Scrubber media we suggest
#8-12 mesh Sofnolime. In warm water, the media should last 16 hours with the standard scrubber, with appropriate adjustments made down for cold water (12 hours). By carefully logging you scrubber media, you will determine how long the media lasts in your dive environments. Scientific studies are being conducted this year that will give more accurate predictions of scrubber break through times, and how it is affected by temperature. With this in mind, we suggest a conservative approach be taken with regards to scrubber duration.