Scuba Safety Stop :Minimizing Decompression Risks
Safety stop is an essential part of the dive when scuba diving , completed at the last 3 minutes of the dive at 3 meters/15th.
It is highly recommended to complete a safety stop at the end of each dive. Find out everything your need to know about the safety stop procedure here.
What is a Safety Stop?
When breathing compressed air underwater, we accumulate Nitrogen in our blood and tissues. Deeper and longer dives mean more Nitrogen we absorb in our tissue. As we ascent to shallow water, excess N2 starts to dissolve from our tissues, as a result of decrease pressure applied on us by the surrounding water.
Confused? Imagine a soda bottle opened up. Changes in pressure allow CO2 to leave the liquid. Our body, in a much smaller scale acts the same. Ascending we reduce that pressure allowing N2 to wash out. If we ascend to fast we risk forming bubbles in our tissues and blood vessels as a result of excessive pressure differential, much the same way as when shaking the soda bottle before opening it up. N2 bubbles trapped in our buddy are dangerous and effectively lead to Decompression Sickness.
A safety stop is simply a stop on the way to the surface where you can still enjoy your dive, as long as you stay at around 5m/15ft for the last 3 minutes of your dive.
By staying shallow for a while we start off-gassing already, though at a much slower rate than at the surface. Back to the soda bottle, instead of opening it rapidly we only twist the cover a bit, allowing some gas to escape.
When to complete a safety stop?
It’s highly recommended to perform a safety stop at the end of each dive, no matter how deep of long. There are dives you must complete a safety stop:
1. When diving to 30m/100ft or deeper.
2. When reaching 3 pressure groups from the No Decompression Limit (NDL) or worse on the Recreational Dive Planner (RDP).
Emergency Safety Stop
In these cases complete a longer safety stop than normally:
1. Diving 1-5 minutes longer than the NDL – complete an 8 minutes-5m/15 ft safety stop.
2. Diving longer than 5 minutes longer than the NDL – complete a 15min 5m/15ft safety stop.
3. If you miss track of time or depth, your timing device or computer fails, immediately yet slowly ascend to 5m/15ft and complete a long safety stop.
Safety Stop Equipment:
1. In high seas or when a diver isn’t comfortable with his buoyancy it’s recommended to use a line to be able to hold on to, and stay at the desired depth for the duration of the safety stop.
2. Safety stop drop tank. On deep dives, and generally a good practice it’s recommended to place an extra tank, known as a dropped tank at the safety stop depth. The tank is turned on than off leaving some air in the regulator attached to it. The idea is to have some air in case you accidentally run out off air, allowing you to still complete the safety stop independently. This dropped tanks’ valve shouldn’t be left opened as the regulator might free flow when flipped upwards.
When reaching the drop tank the may have air still trapped in the regulator good for one breath of air, leaving enough time to open the tanks valve and secure himself to the tank.
3.Safety stops extra weights: as mentioned before we tend to be more buoyant at the end of the dive, with a near empty tank, in shallow water. Some Scuba Instructors and Divemasters may grab some extra weights just for that, but you may also place extra weights secured to the ascend line, drop tanks end others.
4.Waterproof Strobe, Light Stick to indicate the location of the line and the desired depth for a safety stop at low visiblilty or at night.
Safety Stop Tips
1. A Safety stop is a good practice for every dive. Make the best of it and swim to the shallows, where more light allows more colors, corals and fish than deep water do.
2. Its always easier to complete a safety stop with some reference, such as shallow reefs, check for a reference point at 5m/15ft and refer to it instead of you depth gauge.
3. There’s generally more water movement at shallow water. High sea might jerk you up and down. If you’re struggling to stay at the same depth, use a line; make sure you allow your hands to move with the line as your body stays level to avoid depths changes.
Remember, at the end of your dive to slowly ascend at a rate no faster than 18m/60ft per minute