SAC and RMV
SAC and RMV
SAC stands for Surface Air Consumption and RMV for Respiratory Minute Volume. Your SAC rate is to measure the amount of gas consumed in bar while you are breathing for one minute on the surface. While the RMV measure the amount of gas consumed in liters per minute on the surface. Note, in our examples we will use the metric system, meter, bar and l/min.
Keep in mind, that your SAC rate is cylinder specific. If your SAC rate was based on the use of a 12 liter cylinder but you change for example to a 15 liter, than you need to recalculate your SAC rate.
The benefit of knowing how to calculate SAC and RMV rate is that you can use these values during your dive (gas) planning. This is as well for a recreational as for a technical diver an important aspect because running out of gas is one of the most common issues in diving incidents.
Time needed: 4 minutes.
How to calculate SAC and RMV
- Check consumed gas
Check the amount of gas you consumed in bar during the dive or period of measurement, start pressure minus end pressure.
- Note the average or maximum depth
For a complete dive you can use the average depth. For a period of measurement at a constant depth use this depth, both depths are in ATA.
- Determine the time
Use the total dive time for a complete dive or the time, i.e. 10 minutes for a period of measurement at a constant depth.
- Calculate total bar used / total dive time = bar per minute used
i.e. 200 - 150 bar / 10 min. = 5.0 bar per minute used
- Calculate average or maximum depth in ATA
(depth / 10 m) + 1 = Atmospheres Absolute (ATA)
i.e. (20 m / 10 m) + 1 = 3 ATA - Calculate SAC
SAC = (total bar used / total dive time) / (average or maximum depth in ATA)
i.e. (200 - 150 bar / 10 min.) / (20 m / 10 m) + 1
i.e. SAC = 5 / 3 = 1.67 bar/min. - Calculate RMV
RMV = SAC x Cylinder size in liter, i.e. 10 liter, 12 liter, 15 liter
i.e. RMV = 1.67 x 12 = 20 l/min.
To find the answer, determine how many liters you consume at 30 m, 18 l/min x 4 ATA = 72 l/min. Calculate your total gas, 12 x 120 bar = 1440 liter. 1440 / 72 = 20 minutes. The answer is 20 minutes.
It is better to determine your SAC and RMV over multiple dives and under different conditions. i.e. current, warm and cold water, limited and good visibility, effort, at rest, etc. With this approach you will get a more accurate average SAC and RMV rate.
There is no such thing as a best SAC or RMV rate however you see that there is an average RMV of 20 l/min at work and around 15 l/min at rest. But don´t take these numbers as a fixed value, calculate yours and work with it.
SAC stands for Surface Air Consumption and RMV stands for Respiratory Minute Volume.
We wish you a good SAC and RMV calculation, last but not least safe and awesome diving!
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What do you see in the Canaries?
What do you see in the Canarian waters?
We are extremely privileged and proud to say that the Canarian waters have some of the most diverse ecosystems found all around Europe. With water temperatures rarely dropping below a cool 18°C the reefs and wrecks are exploding with marine life.
As Tenerife is just off the western African Coast, in the Atlantic Ocean, the waters are full with exotic and tropical wildlife.
Depending on what kind of dive you would like to do, every dive location has its unique encounters. The Canary Islands are made up of seven volcanic islands, with Tenerife being the largest. With the Islands close to the coast of Africa, the waters contain very low levels of plankton (high levels of plankton reduce water visibility), making the Canarian waters some of the clearest in the world, exceeding 30 meters on days!
Around 553 marine species
There are around 553 marine species that have been documented in the Canary Islands which are separated into 3 categories:
- Cartilaginous fish
- Bony Fish
- Agnatha
With more than 75% of these species living in the coastal zone, you do not have to travel far to be able to experience just how beautiful the waters surrounding the islands are.
The Cartilaginous group of fish is represented by rays and sharks. There are several characteristics that make them different from their bony cousins. Firstly, they do not have a calcified cartilaginous skeleton. They also breath through separate gill openings and finally they generally have a thick skin without scales. During reproduction, both species a process called Viviparous takes place. This is where the egg of the animal hatches inside the mother.
The Bony fish group are the largest group of fish. As their name makes clear, they have bony skeleton that allows them to control their buoyancy and maintaining stability. Around the Canary Islands, no matter what dive you do, you will find yourself surrounded by this beautiful category. Some include, the trumpet fish, breams, flounders and the beautiful but misunderstood Moray Eels!
The huge category of fish is then broken down into 3 more sub-sections;
- Pisciform Fish
- Flat Fish
- Serpentine Fish
We will cover these sub sections in a future blog!
The third group is the Agnatha fish, these are known as
the jawless fish. These include the hagfish and Lampreys.
Interested in learning
If you are interested in learning beyond being told what you see then, without a doubt, I recommend you to do the ‘Underwater Naturalist Specialty’. This specialty focuses solo on learning about the Aquatic life you
find around these beautiful waters.
The waters around the Canary Islands do not have any species that can cause you real harm. However, as with every dive you must be careful and watch where you put your hands.
There are a few things you must look out for before diving. This includes, fireworms, scorpion fish and, Sea urchins although, if left alone, will cause you no harm. With stingrays and sharks, as with any species of animal, if you respect them and do not touch (which we cannot tell people enough, do not touch any animal) then diving in Tenerife has no real wildlife dangers.
Scubapro Cares
What we love about Scubapro and PADI, is how passionate they are about preserving our oceans. We are a dive center for the future and without companies and organisations like ‘Scubapro Cares and Project Aware’, the oceans will become less and less diverse.
As we dive around the islands you will find hundreds of different types aquatic species. This includes 7 different types of stingrays and 5 types of turtles (there are only 7 species of turtles around the world).
Underwater photography
If you love photography then we cannot stress how amazing the Canary Islands are for up close and distance photos. The numerous number of Nudibranchs allow some of the most beautiful Macro photography we have ever seen. Every year competitions take place where divers from around the globe come to participate, with some jaw dropping results.
A specialty we always recommend to divers, is the ‘Digital Underwater Photography’ specialty. Capturing your experiences under the waves is such an incredible experience. Taking a picture underwater is simple, however, taking an amazing picture takes a little work. This course focuses on the Micro and Macro images.
Canarian waters sunken mystery’s
The waters are not just full of marine life, but the Canaries also have some beautiful sunken mystery’s that are home to even more of our watery friends!
One wreck that we will definitely write more about is a tug boat called ‘El Peñon’. This ship was sunk for the primary purpose to bring the aquatic life back to the waters that surround the town of ‘Tabaiba’. It has done an incredible job and it is an amazing example on how human interaction can
have a positive effect on our fragile ecosystems. This is one of the specialties that our team stands out in. With over 15 years of diving the unforgiven Black Sea. Our team has explored arguably some of the toughest wrecks in the world. If you want to explore wrecks safely and correctly then please check out our ‘IANTD Wreck Diving specialty’.
With over 500 species of marine life and numerous wrecks in the Canarian isles, I will confidently say that diving here is an incredible experience. Every dive brings you different encounters and I firmly believe that we have some of the best diving locations in all of Europe.
If you have any questions about ‘What you will see’, please contact us through our website and we will be more than happy to provide you with information and answers.