How Deep Can You Dive Without Decompression Stops? NDL Explained
Deep diving may be done as part of recreational diving or to explore old ruins at the bottom of the ocean. Regardless of the purpose, when you dive deeper it becomes trickier and has greater risks involved as opposed to performing shallow dives when you’re scuba diving. To avoid the buildup of compressed gases in the body, scuba divers have to make decompression stops as they return to the surface.
How deep can you dive without decompression stops? There are a number of factors that come into play: Previous Dives, Gas mixes used, Length of dive, to just name a few. All these impact the depth you can dive down to before you have to make a decompression stop.
- 1 What is Decompression?
- 2 How Does a Diver Decompress?
- 3 What Are Decompression Stops?
- 4 The Non-Decompression Limit (NDL): Diving Without Making Decompression Stops
- 5 Is There a Maximum Depth for Non-Decompression?
- 6 Do You Need a Special Certification for Deep Dives?
- 7 Considering the Use of Nitrox
- 8 Safety First
What is Decompression?
Decompression simply defines the process of releasing pressure or compression. Scuba diving (recreational diving or technical diving) places you in a high-pressure environment, and as you go deeper, the water pressure increases.
In fact, the water pressure increases by 14.5 psi (unit to measure psi) after around every thirty feet. Atmospheric pressure at sea is around 14.7 psi.
It doesn’t take a scientist to understand that the deeper you go, your body will have to deal with the pressure that is two or three times greater than what you’re used to. Sea creatures have flexible and lucid bodies, which help them deal with the water pressure, but our bodies are not designed the same way.
This is about to get a little scientific, but just stay with us: essentially, the compressed air that you breathe in is a combination of nitrogen and oxygen (much like the air you breathe in on land).
The more time you spend underwater, the more compressed nitrogen you take into your body. This is because the water is denser than air and the inhaled nitrogen takes longer to escape through our skin. The higher the nitrogen content in your body, the more time it will take to escape your body and decompress.
As you ascend, the water pressure decreases, and the nitrogen finds it easier to escape from your body. However, if it escapes too fast, you become prone to decompression sickness (The Facts about Decompression Sickness). So how exactly do scuba divers decompress without exerting their bodies too much?
How Does a Diver Decompress?
Divers decompress by slowly returning to the surface. As you ascend, the compressed nitrogen slowly releases from your body. If you ascend too fast, these gases will also escape fast and create bubbles. Nitrogen bubbles are likely to lead to decompression sickness.
What is Decompression Sickness?
Decompression sickness is characterized by joint pains, knee cramps, and other body pains. In the worst-case scenario, it can potentially lead to heart trouble and death.
The buildup of nitrogen bubbles in your bloodstream can damage your blood vessels and rupture the flow of blood in your body. This may lead to heart attacks, heart failure, and even paralysis.
Therefore it is essential to ascend slowly. Your scuba dive computer can help you regulate your ascent rate to avoid the formation of nitrogen bubbles.
What Are Decompression Stops?
To avoid the problem of decompression sickness, divers make decompression stops during their ascent. These stops are an opportunity for any gas bubbles that have already formed to escape.
Deco stops are necessary for deep divers. Not making these stops can be detrimental to a diver’s health.
What is a Safety Stop and How Does it Compare to a Decompression Stop?
Safety stops usually last around five minutes and are required for anyone diving to a depth of around 15 feet. They are more of a precautionary measure and even if you miss one, it is not likely to be harmful.
For divers going deeper than 15 feet, safety stops are a must. Once you’re done with your scuba dive, as you ascend, you need to make a safety stop after around every five minutes.
The Non-Decompression Limit (NDL): Diving Without Making Decompression Stops
Put simply, the Non-Decompression Limit, short NDL, is the depth at which you can dive and ascend from without making deco stops. This limit varies, based on your diving history and the depth to which you’re going.
If you’ve dived earlier in the day, your body is likely to have residual nitrogen. If you go for another scuba dive, your tolerance for compressed nitrogen will be lower and decompression sickness is likely to occur in a shorter time period.
Staying underwater beyond the NDL means that a diver needs to make decompression stops while resurfacing to avoid the risk of decompression sickness.
In fact, a diver should never exceed the NDL unless they have the appropriate training on how to make deco stops.
What Determines the NDL for a Dive?
The nitrogen levels in your body determine the NDL for a dive. If you’ve absorbed too much nitrogen during your dive, you cannot ascend without making decompression stops.
This is because the more nitrogen there is in your system, the more likely it is to escape in the form of bubbles, which will lead to decompression sickness.
How Do You Know How Much Nitrogen You Absorbed?
The nitrogen content in a diver’s body is dependent on a few things:
- Time spent underwater: the longer your dive, the more nitrogen you are likely to absorb.
- Depth: the deeper you go into the water, the more nitrogen you’re likely to inhale due to the increased water pressure.
- Gas tank content: the tank you have with your scuba gear can have different ratios of oxygen and nitrogen. If you opt for a tank that has a higher nitrogen content, you will absorb more nitrogen in a shorter period.
- Diving history: nitrogen remains in a diver’s body even after the dive is over. If you’re doing more than one dive in a day, you’re likely to reach your decompression limit faster after the first dive. This limit will come in shorter periods of time as the number of dives goes up.
If you consistently use the same dive computer then it will take care of all these factors. It keeps your dive history with all relevant information and will take these into consideration when giving you guidance on safety and deco stops.
Is There a Maximum Depth for Non-Decompression?
Let’s look at the details of diving without making deco stops. Pretty much all dives are decompression dives because in all cases, your body will dispel compressed gas as you return to the surface.
The question remains, how deep can you dive without making any decompression stops?
Decompression stops are dependent on 2 variables:
- The depth you dive to
- The amount of time you spend underwater
This simply means that you can spend more time underwater at shallower depths than if you go for a deep dive. The compressed air will escape your system before you need to make a decompression stop. This doesn’t change the fact that you still need to return to the surface slowly to avoid any sudden buildup of gas bubbles.
Diving to depths of around 80 feet means you will have less time to spend at that depth because you need to save time and energy for your deco stops on your way back up.
Here are some estimates of the depth and duration of dives you can make without making decompression stops. Keep in mind that these estimates to dive without decompression only consider the first dive of the day and the values will significantly change if you’ve already gone for a dive or two earlier on in the past 24 hours.
- At a dive depth of 15 meters, you can go for around 70-80 minutes without having to make a decompression stop.
- At a dive depth of 30 meters, you have an NDL of around 20 minutes.
- At a dive depth of 50 meters, your NDL will only last for around 8 minutes.
Crossing these time limits for the given dive depth will mean that you need to make a decompression stop/s as you ascend. You will notice that as the dive depth increases, the time you can spend underwater to dive without a decompression stop significantly decreases.
If you do need to make decompression stops, you will also have to consider factors such as how much air you have left in your tank. This is because you will require air to breathe at your deco stops as well so you can’t use it all up during your descent.
Do You Need a Special Certification for Deep Dives?
In order to deep dive, you need to have special certification (How Many Scuba Diving Certifications Levels are there that You need?) and training to:
- Understand how and when to make decompression stops,
- Read your dive computer for the rate at which you should ascend and,
- How to regulate your air supply underwater.
Scuba diving to a depth of 18 meters or below is considered deep diving. The greatest depth you can go to without special certification to dive deeper is around 40 meters. Any dive deeper than that requires special certification.
In order to be a certified deep diver, you need to be older than fifteen years and at least have an Open Water Diver certification.
The deep-diving certification will equip you with knowledge of how to properly use your diving equipment, regulate your air supply, and other information to have a safe dive.
Considering the Use of Nitrox
Nitrox diving simply involves using a gas mix that has a greater oxygen content. It can help you increase your dive time, but in order to become a Nitrox diver, you need to have proper certification.
Deep dives can be an incredible experience because it lets you explore the depths of the ocean and all its mysteries. All you need to do is take the right precautionary measures to ensure that you avoid the risk of decompression sickness.