News
Rebreather Pre-Dive Checks
The following is a discussion and review of the subject of Pre Dive checks when diving rebreathers – a much discussed, varied and often controversial matter!
When we first learn to dive, the concept of a buddy check, pre dive check or safety drill is installed in us as a means to make the dive safer by spotting potential problems before they can manifest and potentially evolve into accidents.
This is not a procedure limited to diving, it is extremely common in the Aviation, Aerospace and military communities, but to bring it closer to home it is present when we drive a car. When we drive a simple, mainly mechanical, car we are aware of the pre drive steps of checking the coolant level, the tyre pressures and the oil level and then adjusting the seat, wing and rear view mirrors to the individual driver. In a more modern, computer controlled car, many of these checks may be completed by the control system and communicated to the driver via dash board instrumentation and at the high end, even the seat and mirror settings can be altered to individual drivers with the push of a button. What is most common is a combination of automated computer generated checks and manual human checks; either way we are assured of the functionality of the vehicle before heading out on the road.
With rebreather technology the source of the pre dive check sequence and method could come from a variety of places. The manufacturer of the specific rebreather, a training agency that teach a specific rebreather, a generic training agency rebreather check list to suit all rebreathers and a learnt acronym to prompt the required checks.
Of course it would be best if available to use the specific rebreather check list or system supplied by the manufacturer.
Within the above there are different ways to complete checks:
- A written check list
- A check list acronym – e.g a common rebreather check list reminder is the acronym of F.L.A.G.S.
- Flow
- Loop
- Analyse
- Gauges
- Stack/Sensors
- Electronic check lists within the rebreathers display
- Electronic check lists that analyse data from the actual components of the rebreather.
What should be checked?
Pre-Assembly
Mushroom (One Way) Valves. The one way check valves within the Mouthpiece assembly that ensure the gas flows around the rebreather in a single correct direction should be tested to ensure they open with and close against FLOW.
The Oxygen, Diluent, Single supply gas and all bailout cylinders for the planned dive should be ANALYSED.
The absorbent canister (STACK) should be either re-packed or replaced. Or the used time of a previously used canister should be noted and the remaining time available compared to the dive plan.
Pre-Dive
There are as many pre dive check sequences as there are rebreathers, in fact many more! So for initial discussion of the steps of pre dive checks we will here use the acronym FLAGS as a starting point. Although not exhaustive if the printed check sheets or on screen check prompts of most of the currently available rebreathers are reviewed all steps within them can be classified under one of the following prompt words:
F – FLOW
Ambient pressure gas flow around the rebreather in a single correct direction. Tested with the Mushroom (One Way) valve check as part of Pre Assembly. This should be tested prior to each dive as stray granules of absorbent etc could compromise a Mushroom Valve.
High pressure and intermediate pressure gas flow around the rebreather. Slowly turn on the cylinder valves and then add Diluent and Oxygen manually, inflate and check dumps on BCD/wing, check that the ADV and BOV function and ensure the solenoid can inject oxygen where applicable to each specific type of rebreather.
L – LOOP
Conduct a negative loop test and a positive loop test where appropriate to each style of rebreather.
A negative test is conducted on a completely assembled rebreather by placing the mouthpiece in the rebreather or closed circuit position and breathing in through the mouth (To empty the loop) and out through the nose until the loop is empty and then closing the mouthpiece. A suitable period of time (A minimum of 1 minute) is allowed to pass and the rebreather should maintain that negative i.e. not leak air into to rebreather.
Indications of a good negative can include, crushed breathing hoses, ADV diaphragm remaining concave or in, a lower PO2 than ambient (e.g. Pre negative mouthpiece open PO2 0.21, during negative mouthpiece closed 0.19) and a strong ‘gasp’ or sucking sound when opening the mouthpiece at the end of the check.
A positive test is conducted on a completely assembled rebreather by placing the mouthpiece in the rebreather or closed circuit position and breathing in through the nose and out through the mouth until the loop is full and then closing the mouthpiece. A suitable period of time (A minimum of 1 minute) is allowed to pass and the rebreather should maintain that positive i.e. not leak air out of rebreather.
Indications of a good positive can include rigid inflated counter lungs.
A – ANALYSE
The Rebreather although containing Oxygen sensors must not be used to analyse the gases used within the rebreather.
All gases, Oxygen, Diluent and all bailouts should be analysed and labeled prior to being assembled into the rebreather or as bailouts with an Oxygen or where required an Oxygen/Helium analyser.
Many rebreathers are calibrated by flushing them completely or flushing a sensing chamber where the sensors sit with Oxygen at Ambient pressure, if this were completed with a gas supply other than specified (i.e. Oxygen) then the calibration would be inaccurate and therefore the PO2 incorrect during the dive.
G – GAUGES
Test the contents of all required cylinders, Oxygen, Diluent and all required bailout and check for leaks.
Turn on (Slowly) cylinder valves and note the reading of pressure.
Turn off cylinder valves and leave off for 1 minute.
Check contents pressure has not dropped (If the pressure has dropped there is an HP or IP leak to be located and resolved)
S – STACK / SENSORS
The rebreather should be tested for basic function by the Pre Breathe detailed below.
The purpose of this check is to watch the 3 sensor outputs for stabilisation, correct reading and change on prompt i.e. whist breathing add Oxygen and note a rise in PO2 and then add Diluent and note a drop in PO2 from set point.
If fitted during the Pre Breathe a Carbon Dioxide sensor can be monitored for a rising figure.
Again if fitted on the specific rebreather a thermal activity monitor ‘Temp Stick’ can be monitored to ascertain the exothermic reaction of the sofnolime absorbing Carbon Dioxide causing thermal sensors within the stack to register a rise in temperature.
Pre-Breathe
The fully assembled Pre Dive checked rebreather should be breathed for an adequate time to assure the user of systems functionality.
This is the period when the above Stack/Sensors tests are performed.
Current research would indicate that a part used, over used, poorly packed, incorrectly fitted or even absent stack may not give enough signs or symptoms of Hypercapnia during a 3-5 minute Pre Breathe to ensure a diver notices and considers the rebreather unfit for use.
Quick Pre Jump Confirmation
Many training agencies provide Pre Jump quick check prompt cards that can be attached to the Rebreather.
Steps on these include but are not limited to:
- Cylinder valves fully open on Oxygen, Diluent, Single supply gas and bailout?
- Electronics on and safe breathable PO2 displayed?
- BCD inflated?
- Mouthpiece in mouth and in rebreather position?
These Pre Jump checks are NOT considered a full Pre Dive check and are in no way meant to replace full Pre assembly, Pre Dive and Pre Dive checks. The Pre Jump is intended to be used in addition to normal checks as a last check just prior to water entry.
Find out more about Phil at www.philshorttechnical.co.uk.
Ho Ho Ho! Vobster Quay’s recording-breaking charity Santa diving event returns on Sunday 15th December 2024 for another round of festive fundraising frivolities. Run in aid of the Royal National Lifeboat Institution (RNLI) and Help For Heroes, this ever-popular annual fundraising event aims to raise sack-loads of cash for these two very deserving charities.
Divers of all levels are invited to grab their Santa outfits – and as much festive cheer as they can muster – and head down to Vobster Quay near Mells, Somerset for a mass sponsored Santa dive in aid of charity. In previous years, the event has attracted divers from the far corners of the UK to join in the festive merriment for a final festive dive before the Christmas and New Year break. Back in 2015, the event smashed the world record for the most Santa divers with 188 divers taking to the waters donning their festive finery – a record that remains unbeaten to this day!
Vobster Santas isn’t just about setting records – it’s also about raising some serious cash for charity. Vobster Quay encourages all divers to get into the spirit of the season to raise much-needed funds for two very deserving charities – the Royal National Lifeboat Institution (RNLI) and Help For Heroes.
Through individual sponsorship and online donations, divers can invite their friends, family and work colleagues to sponsor them to plunge into the balmy waters of Vobster Quay dressed in full festive finery. Since the very first Santa dive in 2007, the event has raised over £52,000 for charity. “It’s been over 17 years since the very first charity Santa dive took place at Vobster Quay and every year the event just keeps getting bigger and better” enthused Vobster Quay owner, Amy Stanton.
“Vobster Santas is a great way for divers to say a massive thank you to the both the RNLI and Help For Heroes – two very deserving charities close to our hearts. We’re immensely proud of all that Vobster Santas has achieved and hope that even more divers will join this year’s event on Sunday 15th December. I’m confident that we can make Vobster Santas 2024 the biggest yet!”.
Divers wishing to participate can get involved by simply registering their attendance at
www.vobster.com/event-vobstersantas.php.
Blogs
Dive into Adventure at Hideaway Beach Resort & Spa: The Ultimate Diving Destination in the Maldives
Tucked away in the remote northern Haa Alifu Atoll, Hideaway Beach Resort & Spa is a premier destination for anyone seeking an unforgettable underwater experience. With over 30 dive sites to explore, divers of all levels can witness the unique and mesmerising beauty of the underwater world. Whether you’re a seasoned diver or new to the sport, Hideaway offers an exceptional diving adventure that is not to be missed.
Explore the Beauty Beneath the Surface
Hideaway is perfectly situated near some of the most spectacular dive sites in the Maldives. The dive school and team at Hideaway offer a very personalised experience to ensure each diver gets an interactive, immersive experience.
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
Unique dive spots such as Theefaridhoo Thila (Heaven and Hell) as one of the 50 best dive sites in the whole of the Maldives, known for its beautiful soft coral gardens.
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
As the resort is located next to a channel which gives guests surprise visits from eagle rays, manta rays, guitar sharks and more.
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
One of the standout features of diving in the Haa Alifu Atoll is the abundance of rare and exotic marine species. The area is known for sightings of whale sharks, manta rays, turtles, and a variety of colorful reef fish. Diving at Hideaway Beach Resort & Spa offers a rare opportunity to encounter these creatures in their natural habitat, creating lifelong memories for guests.
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
Whether you’re exploring deep coral gardens, dramatic overhangs, or vibrant reef walls, each dive offers something new and exciting. The visibility in the Maldives is exceptional, often exceeding 30 meters, making it ideal for both underwater photography and general exploration.
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
Diving for All Levels
At Hideaway, we believe that everyone should have the opportunity to experience the thrill of diving. That’s why we cater to divers of all levels, from beginners to experienced professionals. Our professional dive center, led by expert instructors, offers a range of courses and guided dives. If you’re new to diving, you can start with an introductory course that will teach you the basics of scuba diving in a safe and controlled environment.
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
For more experienced divers, we offer advanced dive courses and guided excursions to some of the more challenging dive sites. Our instructors are knowledgeable and passionate about the local marine life, ensuring that every dive is not only safe but also informative and enjoyable.
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
Exclusive Diving Offer
To make your stay even more unforgettable, Hideaway is offering an exclusive diving package designed to enhance your experience both above and below the water. When you book a minimum 7-night stay, you’ll receive:
- 35% discount on room rates.
- Complimentary diving: 3 dives per person for 2 guests, allowing you to experience the beauty of the Maldives underwater world.
- Free meal plan upgrade: enjoy a complimentary upgrade from Bed & Breakfast to Half Board, or from Half Board to Full Board. Guests who prefer the White Platinum Plan (WPP) can avail it at a discounted rate.
This incredible offer provides the perfect opportunity to experience world-class diving while enjoying all the luxury and comfort that Hideaway Beach Resort & Spa is known for.
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
Combinable Offers for Even More Value
This diving offer can also be combined with our Anniversary and Honeymoon offers, allowing you to create the perfect celebration package. Whether you’re celebrating a milestone or simply seeking a romantic getaway, this offer ensures that you can enjoy the best of both worlds – luxurious accommodations and unforgettable diving adventures.
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
Terms & Conditions
- This offer is available exclusively for bookings made through the official Hideaway Beach Resort & Spa website using a specific booking code.
- The offer cannot be combined with other promotions available on the website or through other channels, nor can it be redeemed for cash.
- All dives are subject to weather conditions, ensuring the safety and enjoyment of all guests.
- Black-out dates: This offer is not available from 24th December 2024 to 9th January 2025.
To book this exquisite offer, use the Promo Code: SCUBA24FD
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
Hideaway is not just a resort; it’s a sanctuary for those seeking peace, adventure, and luxury. With spacious villas, private pools, and world-class dining options, the resort offers everything you need for a perfect holiday. From tennis, golf, gym, cycling to the exquisite underwater activities, unique dining options, Hideaway has something for everyone. And for diving enthusiasts, it provides an unparalleled opportunity to explore some of the most beautiful dive sites in the world.
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
Our dive center is fully equipped with state-of-the-art gear, ensuring that every dive is safe, comfortable, and enjoyable. Our instructors are passionate about the underwater world and are eager to share their knowledge with you, whether it’s your first dive or your 100th.
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
The Ultimate Dive Adventure Awaits
If you’re looking for an unforgettable diving holiday in the Maldives, look no further than Hideaway Beach Resort & Spa. With over 30 dive sites, unique marine life, and exclusive offers, we provide the ultimate underwater experience. Whether you’re celebrating a special occasion or simply seeking adventure, our diving package offers exceptional value and incredible memories.
Book now through our official website to take advantage of this exclusive offer and prepare for the dive adventure of a lifetime.
Email: reservations@hideawaybeachmaldives.com
Call: +960 650-1515
Website: www.hideawaybeachmaldives.com
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