Proper Ascent Rate Control
So why do divers care about ascent rate at all? While many of us are haunted by painful memories of arduously studying dive tables during our training (yes I am that old!), much of what we were taught about nitrogen loading is easily forgotten. Part of this is because dive computers are largely doing the work that used to be the responsibility of our brains. While this makes our dives easier and longer today, it also means divers often over-rely on computers.
It’s important, especially if you aren’t diving often, to review these concepts. These articles here and here are great places to review some of the fundamentals of nitrogen absorption in regular no-decompression diving. That applies to all not qualified as technical divers in the PADI training framework.
When I first learned to dive the ascent rate was 18 metres a minute and that is the same for all divers who were certified before 1996, but then Navy studies found that a slower rate resulted in fewer cases of DCS. Training agencies, including PADI then changed their recommendations.
The ideal rate for ascending is between 9 and 18 metres per minute, the slower the better. You also should be conducting a safety stop at 5 metres for 3 minutes. This article outlines the history of the safety stop and is an interesting read even for seasoned divers.
People often see the thumbs-up sign and think the dive is over or feel pressured to ascend quickly because they are low on air, cold, or are late for a rendezvous time. In reality, you still have quite some time from when you leave the bottom before you are on the surface, depending on the depth from which you are ascending. This needs to be factored into the dive plan before you get in the water. Even with computers, you should mentally calculate how long your ascent should last before you go up.
For example, if a diver is ascending from 18 metres, using a conservative estimate of the ascent rate listed above plus a three minute safety stop should mean the ascent is at least 5 minutes.
Be aware of the type of computer on your buddies wrist and how the diving algorithm works in relation to yours. As an example my computer has no concept of "Deep Stops" but if diving with someone whose computer does and they need to complete a stop, my computer is still diving and therefore this needs to be discussed and put into the dive plan, to stop us from going into decompression stops.
I’ve had the best ever safety stop with seals, use the time to relax and look around. Also remember that the 3 minutes recommended for the safety stop are a minimum. If you’ve got air, it’s perfectly fine to hang out longer.
The saying “plan your dive, dive your plan,” is as appropriate as ever. Proficiency in planning is developed through a combination of theoretical knowledge, skills, and gear.
Best Practise....
Check your Buddy
Don’t lose your Dive Buddy, you should both be ascending at a similar rate. If your buddy is rising rapidly, don’t try to keep up. Instead, try catch his/her attention to let him/her know that they need to slow down.
Divers sometimes panic during ascent, thinking they will run out of air. The panic will often result in faster air consumption and a more rapid rise to the surface – the opposite of what you need to do. Check your and your dive buddy’s air consumption as you may need to share air using your octopus or spare regulator, if they are too low.
Keep Breathing
The number one rule in scuba diving is to keep breathing. This is important throughout your entire dive. Keep this in mind starting from your descent, your actual dive and particularly to your ascent. Holding your breath at any time during your dive can put you at risk of serious lung injuries.
Pressure is everything in scuba diving and must be taken into consideration throughout your dive. When you descend, the lung volume decreases. Meanwhile, your lungs expand while you ascend. This is why you must never hold your breath. Remember that over-expansion lung injuries are serious and can even be fatal.
Computers
Read the manufacturers instructions, setup your computer and ensure you can read and interpret what it is saying underwater.
SMB's
Never attach to your equipment, practise deployment prior to needing to.
BCD's / Wings
Remember your training and the Five Point Ascent and the one button you do not press on an ascent is your Low Pressure Inflate button! The air in your BCD / Wing WILL expand during the ascent...
It’s important, especially if you aren’t diving often, to review these concepts. These articles here and here are great places to review some of the fundamentals of nitrogen absorption in regular no-decompression diving. That applies to all not qualified as technical divers in the PADI training framework.
When I first learned to dive the ascent rate was 18 metres a minute and that is the same for all divers who were certified before 1996, but then Navy studies found that a slower rate resulted in fewer cases of DCS. Training agencies, including PADI then changed their recommendations.
The ideal rate for ascending is between 9 and 18 metres per minute, the slower the better. You also should be conducting a safety stop at 5 metres for 3 minutes. This article outlines the history of the safety stop and is an interesting read even for seasoned divers.
People often see the thumbs-up sign and think the dive is over or feel pressured to ascend quickly because they are low on air, cold, or are late for a rendezvous time. In reality, you still have quite some time from when you leave the bottom before you are on the surface, depending on the depth from which you are ascending. This needs to be factored into the dive plan before you get in the water. Even with computers, you should mentally calculate how long your ascent should last before you go up.
For example, if a diver is ascending from 18 metres, using a conservative estimate of the ascent rate listed above plus a three minute safety stop should mean the ascent is at least 5 minutes.
Be aware of the type of computer on your buddies wrist and how the diving algorithm works in relation to yours. As an example my computer has no concept of "Deep Stops" but if diving with someone whose computer does and they need to complete a stop, my computer is still diving and therefore this needs to be discussed and put into the dive plan, to stop us from going into decompression stops.
I’ve had the best ever safety stop with seals, use the time to relax and look around. Also remember that the 3 minutes recommended for the safety stop are a minimum. If you’ve got air, it’s perfectly fine to hang out longer.
The saying “plan your dive, dive your plan,” is as appropriate as ever. Proficiency in planning is developed through a combination of theoretical knowledge, skills, and gear.
Best Practise....
Check your Buddy
Don’t lose your Dive Buddy, you should both be ascending at a similar rate. If your buddy is rising rapidly, don’t try to keep up. Instead, try catch his/her attention to let him/her know that they need to slow down.
Divers sometimes panic during ascent, thinking they will run out of air. The panic will often result in faster air consumption and a more rapid rise to the surface – the opposite of what you need to do. Check your and your dive buddy’s air consumption as you may need to share air using your octopus or spare regulator, if they are too low.
Keep Breathing
The number one rule in scuba diving is to keep breathing. This is important throughout your entire dive. Keep this in mind starting from your descent, your actual dive and particularly to your ascent. Holding your breath at any time during your dive can put you at risk of serious lung injuries.
Pressure is everything in scuba diving and must be taken into consideration throughout your dive. When you descend, the lung volume decreases. Meanwhile, your lungs expand while you ascend. This is why you must never hold your breath. Remember that over-expansion lung injuries are serious and can even be fatal.
Computers
Read the manufacturers instructions, setup your computer and ensure you can read and interpret what it is saying underwater.
SMB's
Never attach to your equipment, practise deployment prior to needing to.
BCD's / Wings
Remember your training and the Five Point Ascent and the one button you do not press on an ascent is your Low Pressure Inflate button! The air in your BCD / Wing WILL expand during the ascent...