Gradient Factors (GF)

Gradient Factors can be made to sound very complicated but are just two numbers, a high gradient factor (GF) and a low gradient factor.

Both are expressed as percentages and they represent a percentage of the way towards the m-value*. 30/80 are popular gradient factors at the time of writing. In this case the low GF is 30% of the way to the m-value while the high GF is 80% of the way to the m-value.

This means that the first deep stop will be introduced at 30% of the way to the m-value rather than at the m-value itself or, to put it another way, 100% of the m-value. Similarly, a high GF of 80 means that the final stop will not be cleared until the diver is at 80% of the m-value, rather than 100% of the m-value.

This means that the low GF controls the depth of the first stop, while the high GF controls the length of the last stop.

*m-value – The term “M-value” was coined by Robert D. Workman in the mid-1960’s when he was doing decompression research for the U.S. Navy Experimental Diving Unit (NEDU). Workman was a medical doctor with the rank of Captain in the Medical Corps of the U.S. Navy. The “M” in M-value stands for “Maximum.” For a given ambient pressure, an M-value is defined as the maximum value of inert gas pressure (absolute) that a hypothetical “tissue” compartment can “tolerate” without presenting overt symptoms of decompression sickness (DCS). M-values are representative limits for the tolerated gradient between inert gas pressure and ambient pressure in each compartment. Other terms used for M-values are “limits for tolerated overpressure,” “critical tensions,” and “supersaturation limits.” The term M-value is commonly used by decompression modelers.

Help Divers Avoid Injuries

Written by DAN Staff

In the Northern Hemisphere spring is a great time to maintain both equipment and skills in preparation for warmer weather and a busy dive season. As many divers make sure their gear is ready to get in the water, you can help them make sure they’re ready, too. By familiarizing yourself with the most common causes of diving accidents, you can offer tips for effective skills practice.

What causes the most accidents?

Accident analysis data has shown that there are five leading causes of preventable dive accidents and injuries:

Uncontrolled ascents
Ear and equalization problems
Poor air management
Diving beyond personal limits
Failure to adequately plan and perform dives
At least one of these factors is present in the vast majority of reported incidents.

How can you help divers avoid incidents?

A great way to minimize problems is to get divers to practice foundational dive skills. Encourage your students and customers to consider which of their skills need improvement and suggest ways for them to practice these skills. Ascents, buoyancy control, ear equalization and emergency weight release at the surface can all be practiced in the pool. Divers can work on air management and dive planning by calculating their air consumption and planning practice dives with you or an experienced buddy.

What else can you do?

Some dive accidents are caused by unexpected equipment problems. Make sure divers know how to maintain, store and care for their gear. Also suggest they practice responding to different gear failures – regulator malfunction or stuck BCD inflators – by reviewing air sharing skills, freeflow regulator breathing and disconnecting their low pressure inflators underwater. Although not common issues, divers should feel comfortable responding to such events before they get in the water.

For more information about safe diving practices or preventing dive accidents, visit

Dive Fit – DAN (Divers Alert Network)

There are moments when scuba diving feels effortless: drifting over a shallow reef or descending through clear water toward a sandy bottom. But diving can also be strenuous — when swimming against a current or trudging to a dive site loaded down with gear, for example. In these situations divers must be physically able to both handle themselves and assist their dive buddies if necessary.

What Does Fitness for Diving Mean?
When determining fitness to dive, a physician may weigh several factors, including the diver’s:

  • Training and experience
  • Current exercise regimen
  • Overall health
  • Diving location (water temperature and possible weather and sea conditions)
  • Type of diving (boat or shore)


A diver who is fit to dive from a boat in tropical water may not be fit to shore-dive in cold water. Similarly, an older diver who maintains a healthy weight but lacks physical strength might be better off avoiding diving in more challenging conditions. Ideally, every diver should maintain a healthy weight and exercise for at least 30 minutes per day. At a minimum, divers need the strength and cardiovascular capacity to successfully manage scenarios such as:

  • Swimming against a current
  • Towing a dive buddy on the surface
  • Helping another diver out of the water

Some divers think of scuba diving as a workout. But diving in the absence of other exercise is not considered sufficient for maintaining an appropriate level of fitness.

Risks for Divers Who Are Not Physically Fit

Divers who are not physically fit risk not only their own lives but their dive buddies’ lives as well. When moments matter, a dive partner should be able to help a fellow diver back to shore or onto a boat to receive first aid.

There is not a clear correlation between obesity and a greater risk of decompression illness (DCI), but divers who are overweight are at greater risk for cardiac emergencies. The most recent Divers Alert Network® (DAN®) Annual Diving Report found that 74 percent of divers involved in fatal dive accidents were overweight or obese (in cases where the victim’s body mass index was known).

Getting Fit to Dive

The Centers for Disease Control and Prevention (CDC) recommend that adults engage in 2.5 hours of moderate-intensity aerobic exercise per week and engage in muscle-strengthening activities involving all major muscle groups two or more days per week. Choosing a mix of activities prevents boredom, and finding a workout buddy can make exercise more fun.

Some exercise is better than none at all, and workouts don’t have to take place in a gym. Walking and swimming are two of the numerous alternatives to exercising in a gym. Swimming can help divers improve their stamina for surface swims, and an analysis by researchers at University College London that studied nearly half a million people for an average of 11 years found that walking reduced the risk of cardiovascular emergencies by 31 percent.

All divers are encouraged to see their physician for regular check-ups. Divers 45 and older should get a dive physical including a cardiac stress test every year. Cardiovascular disease is the No. 1 killer for people age 45 years and older, and a dive physical can detect serious health problems such as high blood pressure before it’s too late.

5 Easy Steps for Maintaining Your Reg

A modern regulator is an extremely reliable mechanism. So reliable, in fact, that some divers will take their regulators on countless dives and never so much as rinse them off. Yet they keep on delivering air year after year.

While this is indeed the modus operandi for the maintenance-challenged individuals among us, the truth is, a regulator is a pretty hefty investment, and when you spend that much on something it kinda makes you want to take care of it. We’re not talking a major commitment here; we’re talking a few minutes after each day of diving following some simple steps to help extend the life and performance of what is really the most important component of your life support system.

This is all it takes:

1. After a day’s diving, making sure the dust cover is in place, give the regulator a quick rinse with a low-pressure hose to knock off any big chunks of dirt, sand or salt
2. Drop the regulator in a bucket of fresh water or the bathroom sink and let it soak for 10 minutes or so
3. During the soak, swish the second stage around in the water (without depressing the purge button) to get water flowing through the mouthpiece and exhaust tee
4. Pull the regulator out of the water and give it another gentle rinse, making sure you hit all swivels and hose connections. This will require pulling back the hose protectors — if your regulator has them — so you can get at the connections to the first stage
5. Give the first stage and second stage a gentle shake to clear any excess water from the yoke and the exhaust tee. Then lay it loosely coiled out of direct sunlight to dry

How to Equalize- featured from DAN (Divers Alert Network)

From simple cases of swimmer’s ear to the serious and sometimes lasting damage of barotrauma, divers are vulnerable to ear problems because the delicate mechanisms that govern our hearing and balance just aren’t designed for the rapid pressure changes that result from diving.

Fortunately, ear injuries are preventable.

Your middle ears are dead air spaces, connected to the outer world only by the Eustachian tubes running to the back of your throat.

If you fail to increase the pressure in your middle ears to match the pressure in your outer and inner ears, the result is painful middle ear barotrauma, the most common pressure-related ear injury.

The key to safe equalizing is opening the normally closed Eustachian tubes. Each has a kind of one way valve at its lower end called the “Eustachian cushion,” which prevents contaminants in your nose from migrating up to your middle ears. Opening the tubes, to allow higher-pressure air from your throat to enter your middle ears, normally requires a conscious act. Swallowing usually does it.

You equalize your ears many times a day without realizing it, by swallowing. Oxygen is constantly absorbed by the tissues of your middle ear, lowering the air pressure in those spaces. When you swallow, your soft palate muscles pull your Eustachian tubes open, allowing air to rush from your throat to your middle ears and equalize the pressure. That’s the faint “pop” or “click” you hear about every other swallow.

Scuba diving, however, subjects this equalization system to much greater and faster pressure changes than it’s designed to handle. You need to give it help.

All methods for equalizing your ears are simply ways to open the lower ends of your Eustachian tubes, so air can enter.

Methods Used:

requires no effort
Typically occurs during ascent.

-Voluntary Tubal Opening
Tense Your Throat and Push Your Jaw Forward
Tense the muscles of the soft palate and the throat while pushing the jaw forward and down as if starting to yawn. These muscles pull the Eustachian tubes open. This requires a lot of practice, but some divers can learn to control those muscles and hold their tubes open for continuous equalization.

-Toynbee Maneuver
Pinch Your Nose and Swallow
With your nostrils pinched or blocked against your mask skirt, swallow. Swallowing pulls open your Eustachian tubes while the movement of your tongue, with your nose closed, compresses air against them.

-Frenzel Maneuver
Pinch Your Nose and Make the Sound of the Letter “K”
Close your nostrils, and close the back of your throat as if straining to lift a weight. Then make the sound of the letter “K.” This forces the back of your tongue upward, compressing air against the openings of your Eustachian tubes.

-Lowry Technique
Pinch Your Nose, Blow and Swallow
A combination of Valsalva and Toynbee: while closing your nostrils, blow and swallow at the same time.

-Edmonds Technique
Pinch Your Nose and Blow and Push Your Jaw Forward
While tensing the soft palate (the soft tissue at the back of the roof of your mouth) and throat muscles and pushing the jaw forward and down, do a Valsalva maneuver.

-Valsalva Maneuver
Pinch Your Nose and Blow
This is the method most divers learn: Pinch your nostrils (or close them against your mask skirt) and blow through your nose. The resulting overpressure in your throat usually forces air up your Eustachian tubes.

But the Valsalva maneuver has three problems:

1. It does not activate muscles which open the Eustachian tubes, so it may not work if the tubes are already locked by a pressure differential.

2. It’s too easy to blow hard enough to damage something.

3. Blowing against a blocked nose raises your internal fluid pressure, including the fluid pressure in your inner ear, which may rupture your “round windows.” So don’t blow too hard, and don’t maintain pressure for more than five seconds.

Swallowing—and various methods of equalizing—are all ways of opening the normally closed Eustachian tubes, reducing the pressure differential between the outer ear and inner ear. The safest clearing methods utilize the muscles of the throat to open the tubes. Unfortunately, the Valsalva maneuver that most divers are taught does not activate these muscles, but forces air from the throat into the Eustachian tubes.

That’s fine as long as the diver keeps the tubes open ahead of the exterior pressure changes. However, if a diver does not equalize early or often enough, the pressure differential can force the soft tissues together, closing the ends of the tubes. Forcing air against these soft tissues just locks them shut. No air gets to the middle ears, which do not equalize, so barotrauma results. Even worse, blowing too hard during a Valsalva maneuver can rupture the round and oval windows of the inner ear.

To learn more, please visit to view the Smart Guide on Ears


Feeling a bit lost? Not sure how to take your diving to the next level? At TEKCamp 2018 – the world’s most popular tech ‘masterclass’ event – we can help you to discover the direction and purpose you need to make your new years diving ambitions a reality…

TEKCamp 2018 will transform your diving – your skills will be sharper, your confidence will sky-rocket and you’ll be a far safer diver!

You’ll gain the essential knowledge you need to decide the training path that best suits your diving aspirations. Sidemount or twinset? Open circuit or rebreather? Cave or deep wreck? And which training agency? We’ll help you chart the path that works for you…

So start 2018 with a positive step that will change your diving forever – book your space at TEKCamp 2018 today! Visit: for more information!

What’s the Difference Between PADI Open Water Diver and Advanced Open Water?

You may have heard your instructor mention the PADI Advanced Open Water (AOW) Diver course, or seen the schedule courses on our events calendar. You may have even thought about enrolling in the course. But are you still wondering how the AOW course differs from the PADI Open Water Diver (OWD) course, and what new things you will learn and experience? If so, keep reading.

The PADI Open Water Diver course: Learning to dive

What happens in the course?

You learn the fundamental skills needed for diving. During the course, you read, watch videos, take quizzes, and demonstrate mastery of basic scuba diving skills.

Parts of the course:

The PADI Open Water Diver course consists of 3 main portions: Knowledge Development, Confined Water Dives and Open Water Dives. You can choose one of three ways to complete your Open Water Diver Knowledge Development.

Why take the course?

The underwater world holds some of life’s most incredible experiences. We have listed 10 Reasons to Become a Scuba Diver, but essentially the OWD course will allow you to become a certified diver.

The Advanced Open Water Diver course: Go on dive adventures

What happens in the course?

The AOW Diver course is comprised of five different Adventure Dives. An Adventure Dive concentrates on a particular activity or skill within the realm of scuba – it is the first dive of a Specialty Diver course.

There are 26 PADI Adventure Dives to choose from.

While you’re doing your AOW dives, you will be accompanied by a PADI Professional. They are there to answer questions and help you fine-tune your technique and learn new skills.

The dives in the AOW Diver course are very different from those in your OWD course. The Adventure Dives are similar to a regular dive, except that you focus on a particular diving specialty. The Deep Adventure Dive of the course involves diving deeper, between 18-30 metres. During the Underwater Navigation Adventure Dive you practice navigation skills underwater while diving.

Parts of the course:

Of the five training dives you complete, the Deep Adventure Dive and Underwater Navigation Adventure Dive are both mandatory. As for the other three dives, you get to choose what interests you the most. Students in the AOW Diver course have very little classroom time and no written exams.

Why take the course?

You will gain more experience diving while under the supervision of an instructor. It is an opportunity to try a sampling of different specialties to see what interests you the most.

Now that you know the difference, are you ready to advance your diving skills.

10 Reasons To Be A Scuba Diver

Why learn to scuba dive? Good question.

There are many reasons to learn to scuba dive. It may be something to mark off your bucket list, a reason to travel or even a way to escape the effects of gravity.

If you have been thinking about it and have not taken the plunge, here is a top 10 list of reasons to learn to dive.

Explore parts of the world that many do not get to see

The ocean covers 71 percent of the earth’s surface. If your goal is to “see the world” then you’ll need to learn to scuba dive.

You have a place to escape everyday technology and Zen out

There are no phone calls to answer or emails to respond to underwater. Your attention is focused on breathing and what you see through your mask (which most of the time is pretty awesome!).

Experience weightlessness

Is gravity always bringing you down? Learn to dive and feel the sweet spot of neither sinking nor floating.

Improve your equalisation skills for flights and mountain drives

Once you master equalising your ears on a dive, you can do it anywhere.

Relive the vast amount of history that lies beneath the sea

You can explore wrecks that sit at the bottom of the ocean, including World War ships and planes.

Tank carrying muscles help you be better at bowling


Master of non-verbal communications

Scuba divers learn to communicate underwater without speaking. The “this way to the exit” hand signal is very handy when you want to signal your date that it’s time to leave the party!

Impress others with your newly acquired knowledge

You will learn about Bar and compressed air in your scuba cylinder. Since you know an empty tank weighs less than full tank, you’ll know that a deflated football weighs less than one fully inflated.

You can one-up your friends on social media

This is especially useful if you have a lot of friends who run marathons…

You know that “Keep Calm and Carry On” is a real thing

After you get certified you will understand the importance of making your air supply last. The trick is to breathe slowly and move deliberately. Good advice for the surface too.

Myths and Misconceptions About Peeing in Your Wetsuit

There is a well-worn saying among divers: there are those who pee in their wetsuit, and there are those who lie about it. We’re not 100% sure if that’s true, but there are plenty of myths and misconceptions we can clear up about making the bladder gladder underwater.

Drinking Less Fluid Prevents Having to Pee

It is never a good idea to dive dehydrated. Not only does dehydration increase your chance of decompression sickness, the body is naturally inclined to create urine when submerged in water.

There is a physiological effect called immersion diuresis. When you drop into water that is colder than the ambient air temperature, vasoconstriction (narrowing of the blood vessels) occurs. Extra blood is sent to the central organs, which your body interprets this as a fluid overload. The body signals the kidneys to produce urine and your brain tells you it’s time to drain the main vein. In layman’s terms: warm air + cold water = need to pee.

Here’s one more reason to ensure you drink enough water. When the body is dehydrated, urine has a stronger odor and color. So do yourself (and everyone else on the boat) a favor and stay hydrated!

Just Hold It

Fighting the urge to urinate can lead to a urinary tract or bladder infection, especially for women. This extremely painful condition is not something you want to deal with on a dive trip – especially in a location where the antibiotics needed to alleviate the problem might not be readily available. So let it go, let it go.

Urine Damages Your Wetsuit

Under normal circumstances, urine will not break down the seals or glue on a modern wetsuit. Divers using a wetsuit with an insular lining should take extra care to wash their suit with appropriate cleaner after soiling it (we hope you will do this regardless). While urine won’t damage a wetsuit, a soiled, unwashed wetsuit can cause a skin condition similar to diaper rash.

Peeing Helps Keep You Warm

Pee proponents often describe how a mid-dive release can make a cold dive much warmer. Unfortunately, the effects are temporary and counter-productive.

Warm urine fools your body into thinking it is no longer in a cold environment. So when cold, fresh water enters your suit, your body isnot prepared. Now you are worse off than before and your body must expend extra energy warming up that cold water.  If fresh water isn’t being introduced, either because your suit has great seals, or you have not “flushed,”  that means you are soaking in your own urine. That’s gross. Here are some better ways to keep warm while diving.

Now that we have covered some myths and misconceptions, let’s talk about some urination etiquette.

Always Flush!

Do not wait until you are walking across the beach or boat deck and get a whiff of something stanky. Take a moment to properly flush your wetsuit. Below are two techniques, consider using both for maximum effectiveness.
1. Grasp the chest of your wetsuit and pull it away from your body a few times.
2. Open the wrist, feet and neck seals on your suit.
3. Repeat.
4. Rotate into a head-down position.
5. Let a stream of bubbles flow from your regulator into your wetsuit via the neck seal.
6. Alternately: use your alternate to “flush” air through your wetsuit.

IMPORTANT: Ensure you have sufficient air supply and good buoyancy control before attempting this method.

How to Pee Like a Pro

Take care of business at the beginning of a dive rather than waiting until the end. This creates a greater opportunity for urine to wash out.

Avoid foods that make urine extra-odiferous such as: asparagus, brussels sprouts, garlic and salmon.
Do not pee in a rental wetsuit consider the human who has to clean it.

Portland Dive Weekend 7-8 April 2018

Looking to gauge interest in a weekends diving in Portland the weekend of 7-8 April 2018.

Two dives a day with Schimitar Boat Charters, shuttle services are being detailed in January, further details to follow.