The lack of a definitive consensus on the ideal scuba ascent rate makes things pretty confusing for people who enjoy underwater navigation. While almost all dive experts agree that scuba divers should ascend slowly, currently, very little evidence exists on what the ideal ascent rate should be. Generally, most of the recommendations come from various observational studies.
If you are preparing for your dive holiday, knowing the maximum ascent rate scuba diving is a good idea. In this article, we will be answering all questions related to the scuba ascent rate.
What is the Maximum Ascent Rate for Scuba Diving?
The usual scuba ascent rate was 60 feet per minute before the United States Navy decided to change to 30 feet per minute back in 1996. Scuba diving agencies later adopted this scuba ascent rate. According to the Navy studies, the slower ascend rate helped reduce the decompression sickness cases.
It is worth noting that the 30-foot per minute scuba ascent rate is not always ideal for the whole ascent. For example, when you are very deep and low on air or approaching hypothermia, making 30 feet per minute your maximum ascent rate scuba diving may not be a good idea. In such a case, you can use a 60 feet per minute scuba ascent rate. However, for the final 60 feet, you should slow down to 30 feet per minute.
Monitoring Your Maximum Ascent Rate Scuba Diving
The ideal way to monitor your scuba ascent rate is via a dive computer. Most dive computers will have an alarm that will alert you when you exceed the programmed scuba ascent rate. The moment the dive computer alerts you that your ascent rate is too high, you should slow down.
If you do not own a dive computer, you can consider using your best dive watch in combination with your depth scuba gauge to monitor the time you take to ascend a specific number of feet. For example, you can use your timing device to ensure that you do not ascend more than 30 feet in 60 seconds.
In rare cases, when you don’t have either a timing device or a dive computer, you can gauge your scuba ascent rate by watching the bubbles around you. You should watch out for tiny, champagne-sized bubbles. Make sure you ascend more slowly than the bubbles.
Another method you may use to estimate your scuba ascent rate is to ascend along a fixed ascent line or anchor line. It is advisable to carry a dive computer or a timing device. Rough approximations are not a good idea.
Why Should You Maintain a Slow Scuba Ascent Rate?
As mentioned earlier, ascending slowly can help you avoid different forms of decompression illness. When you dive, your body will absorb nitrogen gas. Following Boyle’s Law, the gas will compress due to the water pressure and slowly saturate your tissues. If your scuba ascent rate is too high, the gas will expand at a rate that makes efficient elimination from your body impossible.
Decompression sickness can be extremely painful. It can also lead to tissue death. In some instances, it can be life-threatening.
In rare cases, if a diver’s scuba ascent rate is too high, he/she may develop pulmonary barotrauma. This is the rupturing of the alveoli found in the lungs.
Pulmonary barotrauma is one of the worst scuba diving dangers and risks. In the case of pulmonary barotrauma, the bubbles may enter the diver’s arterial circulation, travel through his/her body, and end up lodging in the blood vessels. This can block blood flow.
This type of decompression sickness is referred to as AGE (Arterial Gas Embolism). If a bubble lodges in the brain or an artery that feeds the spinal column, the diver may end up having impediments or loss of function.
Safety and Deep Stops
In addition to low scuba ascent rate and having the best dive safety gear, safety stops are recommended at 15 feet per 5 meters for approximately 3 to 5 minutes. Safety stops allow your body to get rid of additional nitrogen before your final ascent.
If you are making deep dives, say, 70+ feet, you should consider making both deep and safety stops suited to your dive profile. For example, you can consider making a deep stop at a 50-foot depth if you were on an 80 feet dive. This will help you have significantly less nitrogen in your body when you surface.
A study conducted by DAN (Diver’s Alert Network) shows the significance of deep and safety stops. After measuring the nitrogen saturation in the tissues of divers who ascended at a rate of 30 feet per minute from multiple 80 feet dives, the following results were obtained:
- If a diver failed to make stops, he/she surfaced with the fast saturation tissues being 60% saturated.
- If the diver made a 5-minute stop at 18 feet, the saturation reduced to 35%.
- If the diver made another 5-minute stop at 48 feet, the saturation reduced to 25%.
Making both deep and safety stops even on dives that are within the no-decompression limit can help reduce the amount of nitrogen in your system significantly. This will lower the risk of having to deal with decompression sickness.
The Final Ascent Should Have the Lowest Maximum Ascent Rate Scuba Diving
The surrounding pressure changes more rapidly as you near the surface. When close to the surface, you should consider reducing your scuba ascent rate to even less than 30 feet per minute. This is because the nitrogen in your body will expand more quickly during your final ascent. Ascending more slowly will give your body additional time to eliminate the nitrogen and hence reducing the risk of decompression sickness.
Globo Surf Overview
All scuba divers must use a slow scuba ascent rate. This will help reduce the chances of dealing with all forms of decompression illness. Instead of relying on approximation methods to monitor your scuba ascent rate, you should consider investing in either a dive computer or a timing device and a depth gauge.
On top of ascending slowly, you should consider making deep and safety stops, depending on your dive depth. The stops will help reduce the amount of nitrogen in your system. This will make your scuba dives safer.
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- Ascending From A Dive (deep safety stops and more), Diverssupport.com