Safety stops are one of the key skills that are taught during any scuba diving course, and while some of the safety skills learning during open water scuba diving classes are only for use in emergency situations, safety stops are one procedure which should be considered to be standard practice every time you enter the water with the intent of diving to a depth of below 10 metres. The reason for this is because safety stops can lessen the chances of developing decompression sickness.
Although the most common depth associated with safety stops is 5-6 metres – the point at which divers are told to remain for 3-5 minutes so that nitrogen can be off-gassed, these days the two-phase theory has been popularized. Many divers now incorporate one further safety stop or “deep stop” into dives, especially if they have been diving to a greater depth or are diving very frequently.
In This Guide
Why Are Safety Stops So Important?
Studies have shown that when divers have a deep stop followed by a shallow one, the lowest bubble grades are yielded. This in turn significantly reduces the chances of developing decompression sickness. An example of appropriate safety stops in a dive of 30 metres would be a stop at 15 metres for 2 ½ minutes followed by a second stop at 5 – 6 metres for 3-5 minutes before finally ascending fully.The main reason for a safety stop is to enable the body to offgas, however there are some other benefits too. It also allows divers to look upwards to check hazards, boat traffic and water conditions. Another purpose of the stop is to enable the diver to check that all of their gear has been secured for exiting the water and to fine tune their buoyancy for the final ascent.
What Happens If You Don’t Have A Safety Stop?
Because you are relying on compressed air when scuba diving, nitrogen starts to accumulate inside the bloodstream. This then becomes absorbed into the body’s tissues through the course of the dive. When we begin ascending out of the water, nitrogen is dispersed gradually from the body’s tissues as the air pressure decreases. If you ascend too quickly, the pressure on the tissues reduces extremely rapidly, and the nitrogen tries to escape too rapidly. This means that the pressure differential is greater and this results in nitrogen bubbles forming in the blood vessels and tissues. When nitrogen bubbles are trapped inside the body, the result is decompression sickness.
Decompression sickness has a number of symptoms although they vary between individuals since the bubbles of nitrogen may form in different areas of the body. The classic symptoms include vertigo or a headache as well as fatigue and extreme tiredness. Some sufferers experience pain in the joints, a rash, tingling in their legs or arms, weakness in the muscles or even paralysis. In some rare cases, divers with decompression sickness suffer from shock, respiratory problems and unconsciousness and in very rare cases, death could follow.
These symptoms will appear fairly quickly after the dive is over, with half of all divers who do not correctly follow the safety stop procedure developing the first symptoms within 60 minutes of the dive, 90% developing symptoms within 6 hours and 98% within 24 hours.
What Is The Correct Procedure For A Safety Stop?
Regardless of depth, the procedure for a safety stop should be the same:
- Once the desired safety stop depth has been neared, neutral buoyancy must be established, either by venting or adding air.
- The safety stop must be either performed in a horizontal or vertical position. If horizontal is your chosen position, ensure that your whole body is at the stop depth. If vertical is your chosen position, keep your chest at the stop depth.
- If there is a PVC bar or line from a dive charter boat, use it as your depth reference and hold the bar or line throughout your stop if the water is calm.
- If the water is choppy, you should established the stop depth, achieve neutral buoyancy and then lightly grasp the bar or line, allowing it to slide as it moves through your hand.
What Are Common Mistakes People Make With Safety Stops?
While many divers are accustomed to ascending slowly, with a perfect safety stop when they come to the end of their dive, following the stop they exit the water without thinking about their rate of ascent. Yet, it is also important to pay close attention to the speed at which you ascend to the surface during these last few yards. One of the safest ways to exit the water from your safety stop depth is to vent all of your remaining air from your BC and kick gently up to the surface. This is a safe technique unless you are wear a lot of weight and will eliminate the chance of your ascent being out of control due to expended air. Remember that you should never ascend to the surface following your 5-6 metre safety stop at a speed greater than 18 metres per minute.After reaching the surface, inflate the BC before preparing to leave the water.
How Can Dive Computers Help?
One of the easiest ways to incorporate safety stops into your dive is to use a dive computer which can help you to determine the correct levels at which to make your stops. Many of the top manufacturers of dive computers have actually incorporated the two stop strategy into the algorithms that they use, so it is easy to ensure that you are stopping in the best places to ensure your safety.
Remember that safety stops are not optional and should be incorporated into every single dive that you do which is deeper than 10 metres. Even though it does take time out of your dive, it is well worth it to ensure your own health and safety, to reduce your discomfort, and to ensure that your dive is as safe and enjoyable as possible.