Why do Scuba Divers Ascend Slowly?

Scuba diving is a popular activity that is appealing to many, it is also an activity that requires proper training to maintain safety. Each year, approximately 200 people die worldwide as a result of scuba diving accidents. Knowing how to dive correctly is essential.

Scuba divers ascend slowly because ascending too quickly can cause serious injury or death. Slow ascents decrease the risk of decompression illness by allowing the body to eliminate excess nitrogen. Rapid ascents may also cause lung rupture with collapse (pneumothorax) and reverse ear squeeze.

While it may seem like fun to give a firm push from where you are diving or to kick quickly to the surface, the result can be painful and even life-threatening. In this article, you will learn why scuba divers ascend slowly to the surface.

What Happens to Your Body When You Dive?

Aside from ensuring you have the proper gear for scuba diving, the ascent is one of the most critical parts of scuba diving that does not leave much room for error. Your body has several physiological reactions when your scuba dive. Among these are build up of nitrogen in tissues due to breathing pressurized air and changes in volume of air pockets in body due to pressure difference from the surface.

These natural effects of breathing compressed air at depth can result in unintended consequences under certain conditions. Two of the most common ailments experienced by scuba divers are decompression illness and squeezes. A more rare event called a pneumothorax (sudden rupture of lung lining with air leak and lung collapse) can also occur. Each of these is due to sudden changes in pressurization of the body. (Source: American Family Physician)

Descending

As you dive down, the pressure of the water increases dramatically. The pressure increase depends on whether the water is freshwater or saltwater. As you descend into the water, the air in your body is significantly compressed. As depth increases, each breath from your air tank includes more air volume to offset the higher external pressure. When you ascend, the air expands because pressure decreases. (Source: Abyss Ocean World)

If you have ever been at the bottom of a swimming pool, you have likely felt the pressure in your ears and lungs. This pressure is magnified during a dive. The scuba gear you wear helps to offset the pressurization effects on the air you are breathing; however, the changes on your body are still apparent and need to be kept in mind throughout the dive.

It is also a common misconception that the gear helps your body not to be “crushed” by the water pressure. This is not true. The gear helps you to stay warm and protected while monitoring the amount of air and time you have left for your dive.

A couple of dangerous situations that can happen during a dive are:

  • Crushed by water pressure: Descending into the ocean or any body of water for that matter will exert an increased pressure on your body. As you descend, the pressure increases and forces the air out of your lungs, thereby causing them to cave in. (Source: Sciencing) This doesn’t occur anywhere near recreational scuba diving depths. This is avoidable by not holding your breath at depth. Your regulator will supply you with the correct volume and pressure of air to prevent this, unless you’re thinking about trying to dive to the Titanic! (Spoiler-you can’t.)
  • Squeezes: One common problem that can occur during descent is called a squeeze. This occurs when the pressure changes and affects both your mask area and inner ears. There is extreme pain associated with this ailment, but it usually heals on its own with time. Learn to properly equalize on descent, and ascend slowly to allow pressure to decrease before you feel pain.

When the squeezes occur, the pressure causes your face mask to suction against your face. If you have ever experienced a suction cup on your skin, you likely know how much it pulls at your skin. The face mask pulls at the skin around your eyes, which can cause bruising to occur. In a severe situation, blood vessels in your eyes may even be impacted. (Source: Ocean Scuba)

You avoid ear squeezes by equalizing as you descend. You avoid mask squeezes by exhaling a small amount of air through your nose as external pressure builds. If you experience ear pain on ascent, descend to the point where the pain goes away, and try swallowing your saliva a couple of times. You can gently equalize to open your Eustachian tubes, but don’t add much air or you magnify the problem. You can also try rolling sideways to reposition the trapped air.

This is called a reverse squeeze, and it is miserable if you ascend all to the surface without trying to correct it first. Only one of us has ever experienced this, but she felt bad for 24 hours with severe pain for the first 6 hours.

Why is it Vital to Ascend Slowly?

A scuba tank contains compressed air, not oxygen as commonly believed. Air contains 71% nitrogen, which is inert and goes unnoticed when breathing at the surface. But inhaling it under pressure results in a gradual build up of excess nitrogen in various tissues of the body.

Decompression Illness

One of the most critical moments during a dive is the ascent to the surface. This is the part of the dive that requires careful calculation and patience. If a diver ascends or comes to the surface too quickly, they may face serious consequences, one of which is decompression illness, often referred to as the bends.

  • Bends (decompression sickness): The bends occur when the excess nitrogen in tissues expands too rapidly for your body to eliminate it. This excess nitrogen can form bubbles in joints, many different tissues, and the blood stream. Bubbles in blood vessels can be carried to vital organs and cut off the blood supply. Heart attacks, strokes and death can occur.

The bends affect many parts of your body. Typically, when a diver is suffering from the bends, they will notice weakness or numbness in the arms and legs, dizziness, vomiting, or even losing consciousness. This is a medical condition that needs to be treated by a physician, as it can affect your entire circulatory system, including your heart. (Source: E-Medicine Health)

The current world record for the deepest dive ever is held by Ahmad Gabr. In 2014, Gabr took 12 minutes to descend to 1090 feet, backed by a team tracking him and helping him switch tanks when needed as I describe here.

Some have wondered if you can scuba dive to the Titanic. The decompression time is essentially incalculable but would likely be months. But the diver would die from nitrogen exposure and external pressure well before reaching 12,500.

Reverse Ear Squeezes

If the diver ascend too quickly, the air pressure in the middle ear will cause the ear drum to bulge outwards. This is called a reverse squeeze, and it is very painful. My daughter experienced this in Bonaire and had to skip the next few dives.

  • ReverseEar squeezes: As you descend, the pressure on your eardrums increases. Divers offset that by adding air to the part of the ear behind the eardrum; the middle ear. This is connected to your throat by a small tube (Eustacian tube). Divers can force air through it during descent by closing mouth and nose and trying to exhale. On ascent, this air has to naturally move back through to your throat as it expands.

You can try to fix this by descending slightly until the pain disappears, and then swallow a few times to open the Eustachian tube. If this doesn’t work, you can tilt head with the painful side down and try again. Or go a little deeper and try both.

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As a last resort, descend a little further very carefully equalizing to reopen the tube. Then ascend even more slowly with the affect ear tilted up. Keep in mind your dive time, depth, air supply and dive profiles for the day as you do this.

Rupture of lung with air leak (pneumothorax)

The lungs are constantly changing pressure with each breath. They are also the most affected part of the body when external environmental pressures change, such as when ascending to great heights or diving to different depths. Since water is denser than air, pressure changes in the body occur in much shorter distances. At 33 feet, the body experiences twice the pressure felt at the surface.

  • Pneumothorax: Another potentially life-threatening complication from a rapid descent. The lungs are lined by a thin layer of tissue connect their walls to the chest wall. This layer moves with breathing. If pressure in the lungs suddenly increases, a hole can develop in this layer, allowing air to leak from lung. This occurs in chest injuries, sudden pressure change environments and sometimes without any cause at all.

When a pneumothorax occurs on the surface, the effects can range from nothing at all to severe breathing problems and cardiac arrest. The hole that forms can allow air to build up between layers such that the lung is compressed. Or it may continue to leak causing the hole to enlarge and the lung to collapse away from the chest wall. This means it won’t expand when you try to breath.

If it occurs suddenly underwater due to rapidly increasing pressure, the effects are magnified quite a bit. Once it has occurred, it requires emergency treatment, preferably by trained doctors or EMTs in an ambulance or hospital. There are cases where lives have been saved by inserting a small sharp needle into the chest to allow re-expansion. But if done incorrectly, it leads to greater collapse and worsening condition.

When a pneumothorax occurs or is suspected, the diver needs to continue ascent as safely as possible, preferably with assistance, and then get immediate medical attention. In the image below, you see that the right lung has ruptured and pulled away from the side wall of the chest. The dark area represents air in the lining of the lung, while the collapsing lung is whiter because it doesn’t have enough air to expand it.

An example of pneumothorax from the author’s personal case files. Not a diving injury.

How Do You Ascend Safely?

When a diver begins their ascent, it needs to be carefully planned and executed. It is recommended that an ascent take place in two different stages that are carefully timed and monitored by the diver.

Stage 1 of the Ascent (Decompression Stop)During this stage of the ascent, the goal of the diver is to reach a safe ascent zone. This means they are ascending from a deep dive location and will need to stabilize halfway to the surface. This decompression stop allows the body to reacclimate to the changing pressure gradually. It is recommended that a diver not ascend more quickly than 30 feet per minute. (Source: Scuba Diving) If you have been on an extremely deep dive, you may have more than one stopping point before reaching the surface.
Stage 2 of the AscentThis is the final stage of the ascent and a time to be extra cautious. It may be tempting to rush to the surface when you can see it just above you; however, you need to continue a slow and steady ascent. It is crucial to slowly release air pressure during this final phase of the ascent to ensure you are correctly depressurizing.

How Do You Track Your Ascent?

Most scuba divers use a dive computer to track their dive times and frequency and decompression status. The dive computer provides the diver with information regarding the time left for a safe dive as well as the depth they have reached.

Determination of safety stops, time between dives, time spent at each depth, required surface break, and more are tracked. (Source: Oyster Diving) The safety of your ascent will be dependent upon the tools you use as well as the communication you have with your dive partner. Your depth gauge and dive watch or computer are used in tandem. If you aren’t using a computer, then you will rely on manual dive tables to track these things.

The entire time a diver is making the ascent to the surface, they should consult their dive computer as well as their diving partner to ensure they are ascending at a safe rate and leaving enough time for the dive to be completed safely.

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Any of the following dive computers should be a good choice for for most people:

Each of these options has fantastic reviews, but if you are uncertain about the brand, style, or type, it would be recommended to seek the help of a professional diver. When purchasing a dive computer, you can plan to spend between $200 – $1,500. Do not fall into the trap of thinking more expensive is better because that may not always be the case. Instead, enlist the help of a professional to guide you.

Why Can Snorkelers Ascend Quickly?

Snorkeling is much different than scuba diving because it involves swimming at the surface of the water. They inhale air at surface pressure, and as they descend the air is compressed. When they ascend, it expands only back to the original volume taken in before descent. Therefore, snorkelers do not need to worry about the speed of their ascent. Snorkelers aren’t taking in pressurized air that can expand on ascent or release higher amounts of nitrogen into the tissues.

Final Thoughts

Scuba diving is a favorite activity for many people around the world. While fun and exciting, it requires thorough training to execute a safe and successful dive. The two bookends to a successful dive are the descent and ascent. By following safety precautions and ascending slowly with dive stops along the way, you will ensure an enjoyable – and safe – dive.

The Importance Of Ascent Rate When Diving

When diving, the ascent rate is the speed at which a diver ascends to the surface. This is generally measured in feet per minute (fpm). There are a number of factors that can affect a diver’s ascent rate, such as the type of dive being performed, the depth of the dive, the amount of air in the lungs, and the buoyancy of the diver.

How fast should an ascent be? According to some organizations, an ascent rate of 30 feet per minute can be attained. Decompression sickness can be caused by rapid ascents. Diver’s equipment should be carried underwater. Look for bubbles larger than champagne and ascend slowly rather than straight. If a diver ascends quickly, he may suffer pulmonary barotrauma, which may cause damage to small structures in his lungs. It is critical to maintain a slow ascent rate in order to reduce the risk of developing all types of decompression illness.

It is much easier for a diver to reduce nitrogen levels in their bodies after landing if they make a deep stop based on their dive profile. Decompression sickness and age should be avoided by gradually ascending from all dives. The more shallow a diver is, the less pressure surrounding him changes rapidly as he ascends. If a diver makes a safety stop at 15 feet every time he or she begins an ascent, and a deep stop is necessary when necessary, he or she will further reduce the amount of nitrogen in the body.

In 2012, a rate of 30 feet (9.1 m) per minute was established by the US Navy, the National Oceanographic and Atmospheric Administration, and a few recreational diver training agencies; however, some agencies still use 60 feet (18 m) per minute.

How Slow Do Divers Ascend?

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A should ascend more slowly from his safety stop to the surface if it is possible, even if it is slower than 30 feet per minute. A scuba diver will experience nitrogen dioxide expansion the majority of the time during the final ascent, and allowing his body to eliminate this nitrogen for an additional time will significantly reduce the risk of decompression sickness.

When ascending scuba, it is recommended that you ascend slowly so that you do not cause serious injury or death. When the body is on a slow ascent, excess nitrogen can be removed, lowering the risk of decompression illness. A rapid ascent can also cause a rupture of the pulmonary vein (pneumothorax) and reverse ear squeeze. The tank of a scuba boat is typically filled with compressed air rather than oxygen. Breathing under excessive pressure causes an increase in nitrogen levels in various tissues of the body. Exhaling a small amount of air through your nose as pressure builds around your ears will help you avoid ear squeezes. Diver decompression illness can occur if a diver ascends or comes to the surface too quickly, causing serious consequences.

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When the bends are present, the numbness, dizziness, nausea, and loss of consciousness they cause can occur in a wide range of parts of your body. Ahmad Gabr holds the current world record for the deepest dive ever held by a human. When a pneumothorax occurs on the surface, the effects can be severe, ranging from nothing to a severe case of breathing problems to death. Life has been saved when inserting a small sharp needle into the chest to increase chest volume. A bad design will result in a more severe collapse and worsening of the condition. The ascent and descent of a diver serve as the two most important bookends to a successful dive. Snorkelers don’t need to be concerned about their speed as they inhale air from the surface. You’ll have a lot of fun while remaining safe if you follow safety precautions and gradually ascend with dive stops along the way.

The diver should ascend from more than 60 feet of depth at a rate of 50 feet per minute, and from 60 to 90 feet at a rate of 30 feet per minute. Diving from 90 feet or higher is safe for a maximum of 15 feet per minute. Slow speeds can allow for more graceful movement, as well as energy savings.

Slow And Steady Wins The Race, Even When Descending Into The Depths Of The Ocean.

In addition, it is important not to go too fast while descending, as this can cause bubbles in the gas in the body. Decompression sickness can quickly develop as a result of the bubbles.

What Is Minimum Ascent Pressure?

At a minimum pressure (MAP), it’s time to rise; at a maximum pressure, it’s time to slide. The MAP can and should vary depending on the depth of the hole. A MAP of 50 bar/750 psi is considered adequate in shallow water, but 70 bar/1,000 psi or higher in deep water is considered more appropriate.

How Fast Can You Ascend In Water?

The answer varies by organization in terms of scuba certification. Some organizations state that you can climb 30 feet/9″ to 9 meters per minute, while others allow you to climb faster. Using old PADI dive tables, such as those used by the US Navy, you can achieve a maximum ascent rate of 60 feet per minute.

How To Prevent Decompression Sickness When Freediving

Decompression sickness can occur when a diver ascends too quickly. Nitrogen gas accumulates in the body’s tissues and can lead to this illness, which can be extremely dangerous. Freedivers typically ascend and descend at a rate of one meter per second, which is significantly slower than the rate at which nitrogen gas accumulates in the body. Decompression sickness is a serious issue that can occur if a freediver ascends too quickly.

Why Do Divers Have To Ascend Slowly?

Divers have to ascend slowly to prevent decompression sickness, which can occur when divers come up too quickly. Decompression sickness happens when nitrogen bubbles form in the blood and tissues. These bubbles can cause pain, paralysis, and even death.

If a diver takes too long to ascend, nitrogen gas in his body will grow at such a rapid rate that it will be difficult for him to effectively expel it. Decompression sickness is a serious condition that causes tissue death and is extremely painful. It is critical to maintain a slow rate of ascent to minimize the risk of all types of decompression illness. Divers should slowly ascend from each dive to avoid decompression sickness and age. Even when the dive is no-decompression, diving deep and making safety stops will significantly reduce the amount of nitrogen in the body during landing. Divers should ascend slowly from their safety stop to the surface, roughly 30 feet per minute or less.

It is extremely beneficial for scuba divers to have a mask that allows them to see underwater. This garment is made of thin plastic or metal that is wrapped around the face and then fitted with a headband. A snorkel allows scuba divers to inhale water through their mouths above the surface. The tube is inserted into the nose and is attached to the mask with a strap. Diver aids in swimming without using hands because they use fins. Feet are attached to the soles of the feet via rubber or plastic. A buoyancy compensated device (BCD) is one such device. By wearing the BCD, scuba divers can stay afloat in the water. A waist belt is worn on the waist and aids in the movement of the body.

Maximum Ascent Rate Scuba Diving Padi

As a contributor, you contributed to the piece. With PADI, the rate of ascent can reach a maximum speed of 18 meters per minute.

In most other languages, there has been a shift to a 10-minute delay. So why have all of others changed and PADI haven’t? A claim made from the past may be possible if they do. The cost of these claims is rumored to be more than the total cost of Padi. Depending on the depth, the maximum safe ascent rate can vary. The maximum length is 60 fpm, according to PADI tables. My elevation rises slowly from about 30′ on up to the final stop (typically 15-20′), and it usually takes me about 30 minutes to get to the top.

It’s a foot per 10 seconds on an NDL dive, which is exactly 1/2 the recommendation. Do you accent slowly when reaching 15f in the arm or normally (30f)? Why do I need to deco dive again after repetitive dives? My most serious issue is that I often believe that I don’t have fast accents, which is actually my primary motivation for using a dive computer.

Scuba Diving Ascending And Descending

When scuba diving, it is important to be aware of your surroundings and to know how to properly ascend and descend in the water. When descending, you should always do so slowly and under control. You should also be aware of your air supply and how much air you have left in your tank. If you are running low on air, it is important to ascend to the surface and get more air.

When we descend quickly, we are more likely to squeeze out air spaces in our ears, necessitating a slower descent. We must also take care not to damage the delicate environments beneath our feet. A compass is the best way for a scuba diver to orient himself or herself. After descending, deflate the buoyancy compensator (BCD) and slide it back up. After deflating your BCD and releasing your exhale, you will feel the water begin to sink slowly. When you do not sink, make sure your pants are properly weighted. It is a good idea to equalize your ears once on the ground before descending to prepare them for subsequent equalizations.

The Recommended Max Ascent Rate Is

The recommended maximum ascent rate is 1,000 feet per minute.

Divers should ascend slowly after completing a dive, according to experts in dive medicine. When it comes to ascending rates, there is no direct evidence to support them. Observational studies using Doppler ultrasound are the most commonly cited as having discovered bubbles of poor quality. The U.S. Navy changed its recommended ascent rate in the 1990s to 30 feet per minute. Decompression stress is defined as the amount of inert gas dissolved in various tissues of the body. Bubbles in the air expand as the aircraft approaches and tissues in the veins release air bubbles. venous bubbles travel to the lungs, where they aregassed by the body through breathing.

Decompression stress may be reduced by climbing faster, according to the theory. Excess air can be managed by venting it from the BCD or drysuit during ascent. If the inflator or deflator mechanisms on BCDs and drysuits are not properly maintained, they can allow air to enter the system at a higher rate than intended. It would be advantageous to use a bottom slope, wall, climb line, or other visual or tactile reference source.

Ascent Rates

Ascent rates are the speed at which an aircraft, rocket or other object ascends. Ascent rates can be affected by many factors, such as the weight of the object, the amount of thrust being generated and the density of the air.

Critical Scuba Diving Skills

There are a few critical scuba diving skills that every diver should know. First, it is important to be able to properly clear your scuba diving mask. This skill is critical because if your mask becomes filled with water, it will be difficult to see and could lead to a dangerous situation. Second, every diver should know how to properly use their scuba diving fins. Fins are a key part of propelling yourself through the water and can be used to avoid obstacles. Finally, it is important to know how to equalize the pressure in your ears as you descend. This skill is critical because if the pressure in your ears is not equalized, it can cause pain and could lead to an injury.

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Despite the fact that training appears to be refined and mastered in real-world open water, many scuba divers find that their performance does not replicate what they have learned in training for years. The more they must meet, the more difficult their ‘easy’ skills become, and so they reduce them to raw beginners as soon as they are introduced to new conditions. Andy Davis’ approach is to begin with the fundamentals – one step at a time. Most people are able to hover (even if only in trim) when they concentrate fully on it. When other factors are prioritized in their task loading process, the hover/trim of their vehicles becomes noticeably deteriorating. The goal of skill acquisition is to be achieved when a function becomes an autonomic (Adj – Involuntary/Unconscious) state without impairing the divers’ ability to perform tasks. Divers who have their Tier 3 competency severely reduced must limit their diving until the competence is restored to an autonomic, timely, and dependable level. Divers should only experiment with task loadings to levels that are consistent with Tier 1-3 competency development; this can only be done at an level that is unintrusive. This could be a reaction to increased activity (such as complex navigation or guideline deployment in an overhead environment) or it could be an act of insurgency.

New To Scuba Diving? Make Sure You Breathe Continuously!

It is critical to breathe continuously during scuba diving. It is critical to have this in order to gain competitive advantage in the sport. Regular breathing reduces the risk of nitrogen narcosis, also known as the bends. It is also a good idea not to hold your breath during a medical emergency. In fact, this can lead to breathing difficulties and even death.

Why Do Scuba Divers Ascend Slowly?

Divers ascend slowly to prevent issues such as decompression sickness or spontaneous pneumothorax. Expanding too quickly causes nitrogen to form bubbles in the body before they can be eliminated and increases the volume of air in the lungs too rapidly to equalize properly.

Keep reading as we explain why a slow descent is essential and what it looks like.

Why Can’t Scuba Divers Come up Fast?

Scuba divers cannot come up fast because of these unwanted reactions in the body.

Understanding Boyle’s law sets the foundation for understanding these complications.

The law explains that, in a closed system where temperature and the amount of gas remain the same, the absolute pressure of a gas tends to decrease as the volume increases.

When you apply this to scuba diving, you see that the decrease in water pressure during your ascent relates to an increase in the volume of gas in your body.

This not only affects the volume of air in your lungs, but it can cause gas in other areas of your body to form bubbles that cause complications.

What Happens If You Ascend Too Quickly Scuba Diving?

Your main concerns with ascending too quickly include decompression sickness, collapsed lung, and arterial gas embolism.

Decompression Sickness

Your body absorbs excess nitrogen gas as you descend. The volume of the gas decreases the further you dive, and slowly soaks into the tissues of your body.

Following a specific rate of ascent allows your body to deal with the nitrogen efficiently as it expands. When you ascend too quickly, the nitrogen expands at a rate where it cannot be eliminated, leaving behind small bubbles in your tissues.

Not only is this painful, but it can lead to tissue death and even prove fatal. Your response to decompression sickness plays a part in this, but avoiding it is always the best course of action.

Collapsed Lung

If you ascend too quickly to equalize the pressure in your lungs, you put yourself in a position where your lung may collapse. This happens most often when holding your breath on ascent, and you may be at a higher risk if:

  • Your lungs are weakened by a disease
  • You have previous lung injuries
  • You smoke or have sufficiently irritated your lungs

These conditions lead to the formation of blisters on your lung’s alveoli that easily rupture, even with normal pressure.

Regardless of the cause, if there is a tear in lung tissue it allows air out into the pleural space (between the chest wall and the lung). The pressure here is normally negative, meaning less than atmospheric, but the increased volume of air leads to positive pressure that pushes against the lung, pushing out more air.

Eventually, this causes the lung to collapse in on itself.

Arterial Gas Embolism

An arterial gas embolism refers to any blockage of blood to the organs. This is caused by bubbles in the artery, and it’s a leading cause of death in scuba divers.

This happens when the gas in your body forms a bubble that cannot be eliminated. When these enter arterial or venous blood, usually after pulmonary barotrauma or decompression sickness, they can travel to any organ and cause a blockage.

The bigger worries here are blockages that deprives the brain or spinal column of blood, but this can also affect your:

The blockage usually leads to loss or impediment of function, as well as injury to the affected organs.

Why Do Scuba Divers Exhale and Rise Slowly When Ascending?

By exhaling and rising slowly while ascending, scuba divers limit the chance of the issues listed above. This may not be exciting, and it’s certainly a pain when you’re tired from your dive, but it’s a necessary safety measure.

Scuba divers also use stops at depth and near the surface to safely deal with the buildup of gas in their bodies.

Safety Stops and Deep Stops

A safety stop usually happens at 15 feet (5 meters) below the surface for a period of 3 to 5 minutes. This gives the body time to work with any additional nitrogen while still under the higher pressure of water before your final ascent.

A deep stop is usually added to dives 70 feet (21 meters) or deeper, but it changes based on your dive profile.

The Divers Alert Network notes that divers who ascended at a rate of 30 feet per minute without a safety stop ended up with fast saturation tissues at 60 percent. When the same divers had a 5 minute safety stop at 18 feet, this decreased to 35 percent. When they added in an additional deep stop for 5 minutes at 48 feet, the saturation dropped to 25 percent.

How Do You Ascend Slowly When Diving?

Your final ascent should be the slowest part of your dive. This is when the greatest pressure change per foot of depth occurs, and nitrogen and other gasses expand most quickly at this point.

By taking it slow you allow your body extra time to deal with these gasses and reduce your risk of decompression illness and other issues.

How Fast Should You Ascend While Diving?

You should never ascend faster than 30 feet (9 meters) per minute. This means it can take you a minimum of 5 minutes to ascend after your safety stop.

Preparation

Before you make your final ascent you should make sure the space above is clear of boats. If you notice anything , including a shadow, it’s best to find somewhere else to surface.

Listen for motors from boats, and either wait for them to pass or move if you hear anything.

When you’ve found your area of accent, inflate and release a surface marker so boats other people know where you are ascending.

Making Your Ascent

After your safety stop, start your ascent by kicking slowly and deflating your buoyancy control device.

Deflating your BCD prevents it from excessive expansion as the volume of gas increases. This would cause you to float too quickly. You can also slow your kicking if you find you’re moving too quickly.

Check your dive computer to make sure you’re moving at the right speed.

Surfacing

When you’re close to breaking the surface it’s best to cover your head using your free arm. You should still look for obstructions, but breaking through with your arm protects you from last minute problems like a motorboat speeding across the area.

Inflate your BCD bladder completely the moment you break surface. This helps you stay above the water while you return to the shore or your boat, and you have an easier job getting out of the water.

Source https://aquasportsplanet.com/why-do-scuba-divers-ascend-slowly/

Source https://www.desertdivers.com/the-importance-of-ascent-rate-when-diving/

Source https://oceanthrill.com/why-do-scuba-divers-ascend-slowly/

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