Part 4: Being a Diver IV
What is a repetitive dive and how does residual nitrogen affect the no stop limits on a repetitive dive?
- A dive made while you still have residual nitrogen is called a repetitive dive - If you stay at the surface long enough for nitrogen level to return to normal, next dive is no longer considered a repetitive dive
What is a surface interval and what happens to the dissolved nitrogen in my body during a surface interval?
- A surface interval is the time you spend at the surface between dives - During this time your residual nitrogen level declines
How do I plan dives with my dive computer?
- Activate and scroll no stop limits - Agree on a max depth and note the no stop time for that depth - On a shallow or multilevel dive, you usually have more no stop time that your air will last - Plan you air management - Your air supply commonly limits your dive, watch your SPG and your dive computer - turn your dive based on the first limit reached - Use a computer-based simulator
How do I refresh my dive skills and knowledge after a period of inactivity and, as a new PADI Open Water Diver, after what interval of inactivity is this recommended?
- After six months - Participate in a PADI Scuba Review program - Register for Scuba Tune-up Online
What are the two most common substances that I should refrain from using before diving and why?
- Alcohol - Affects judgement - Accelerates body heat loss - Tends to dehydrate you - may contribute to decompression sickness risk - Smoking - Avoid several hours before and after diving - Theoretically raises the risk of lung overexpansion
Why should I be cautious about attaching a mesh utility bag to my gear while diving?
- Attaching a bag to your gear while diving - You need to be able to quickly discard anything that may weigh you down - Avoid creating potential entanglement or snagging problems
What should I do if I feel ill before a dive?
- Cancel the dive
For what four purposes might I carry a slate or wet block?
- Communication - Note dive plan limits - Record information during the dive - Unexpected - don't always know what you'll need to write
What information do I typically record, at a minimum, regardless of which I choose?
- Date - Dive site name - Dive buddy - Dive depth and duration - Objective & description
What condition can result if I exceed established depth and time limits while diving, and then surface and what happens in the body that causes this condition?
- Decompression sickness (DCS) - Nitrogen bubbles can form within your blood and body tissue
What is the relationship between depth and my no step limits?
- Deeper= more pressure = faster nitrogen dissolved into body tissue - Deeper you dive, the shorted your no stop limits
What two primary factors influence how much nitrogen dissolved into my body tissue during a dive?
- Depth and time
What should I do as a diver if I am or may be predisposed to heart disease?
- Discuss them with your doctor to help assess and manage risk
What are six guidelines for diving with a computer?
- Dive you plan - Stay based on your plan not the computer as it add more no stop time - Stay well within your computer's limits - Follow the most conservative computer - yours or your buddy's - Watch your SPG - Start at your deepest point and go shallower - Ascend slowly and make a safety stop at 5m/15 ft for 3 mins
Why is it important to apply environmentally-friendly dive skills and awareness while underwater?
- Diver damage can destroy the natural beauty - Ecosystems already under stress may struggle to recover from damage - Dive skills that are good for the environment are also good for you
How do I prevent problems with oxygen when diving with air?
- Don't exceed max depth of 40m/130ft
What are the recommendations for using prescribed or over the counter medication before diving?
- Don't use drugs that affect your judgement, thinking or reactions - Consult your physician - If in doubt, don't dive until you no longer use medication
What options can I choose from when choosing mesh utility bags?
- Draw string closure, wire or plastic frame - All mesh or solid upper portion with besh bottom - Hand sized to large enough for most gear
What are four advantages of dive computers over dive tables?
- Easier to use than tables - Help offset human error - Give you more time underwater - Have other useful features
What can I do with dive planning software?
- Estimate how long your air supply will last on a dive - Estimate the time your dive computer will allow on a dive
What factors in diving can strain my heart and cardiovascular system?
- Exertion for swimming hard - Carrying equipment - Climbing a ladder - Long walks wear gear - Heat stress
Besides dive time and depth, what nine secondary factors are thought to influence dissolved nitrogen?
- Fatigue - Dehydration - Cold - Poor fitness and high body fat - Illness - Injuries - Age - Alcohol consumption before or immediately after
What options do I have with dive planning software?
- For desktop/laptop or tablets - Very basic software intended for planning recreational dives or software designed for much more complex, technical diving
How do I avoid contaminated air problems?
- Get cylinder fills at reputable scuba air sources
What are some possible causes of contaminated air?
- Getting a cylinder filled at an improper source - Improper maintenance of the filling system - Very high levels of contaminant in the source gas
Why is my ascent rate an important part of a no stop dive?
- Going faster than your ascend rate is going to increase risk of DCS
What should I do for a diver who I suspect breathed contaminated air?
- Have the diver breathe fresh air and provide emergency oxygen - Provide CPR if required - Contact emergency medical care
What are five possible signs/symptoms of contaminated air?
- Headache - Nausea - Cherry red kips - Dizziness - Unconsciousness
How does using enriched air nitrox affect the component gases that make up air?
- Higher amount oxygen: - 32% nitrogen and 36% oxygen
What would I use a mesh utility bag for?
- Holding litter during an underwater cleanup - Carrying small accessories - Transporting gear to and from the dive boat
What effect does menstruation have on diving and is it recommended that pregnant women not dive?
- If menstruation doesn't normally affect you from doing any other activity it should be an issue - It is broadly recommended that pregnant women don't dive just because the risk is not known and it's not worth the risk
How does continuing my diver training help keep my skills refreshed?
- Keep diving and learning new things at the same time - Acquire new skills and increase your capabilities
What would I use a dive light for and why might I use one during the day?
- Lights are useful for peering into holes and cracks
Why do I log my dives?
- Logged dives provide a reference you can use to plan subsequent dives - Notes about dive sites and equipment - Documentation of types and number of dives is often required for continuing education courses
What general recommendations apply to my fitness as a diver?
- Maintain a reasonable level of physical fitness - Keep your immunizations current - Eat a well-balanced diet - Get adequate rest
What component gases make up air? For practical purposes, what percent of each of the component gases does air consist of?
- Nitrogen (79%), oxygen (21%) and a dozen trace gases
What is residual nitrogen?
- Nitrogen left in your body after a dive - Shortens no stop limits if you make another dive
Does a dive computer or dive table directly assess anything going on inside a divers body?
- No - They apply a mathematical decompression model used for most people
Are divers a significant threat to the overall health of the underwater environment?
- No divers aren't a significant threat to the overall health - Damage caused through poor technique - Intentional interaction has serious environmental consequences - Underwater hunting without restraint - Using toxins to catch fish - Damage to wrecks and other cultural resources
What seven types of information do dive computers tell me before, during and/or between dives?
- No stop limits - Depth - Elapsed time - No stop time remaining - Ascent rate - Emergency decompression - Previous dive information
Why shouldn't I dive with a cylinder labelled "oxygen" or known to be filled with 100% oxygen?
- Only used by technically trained divers
To what four diving related issues does the makeup of air relate?
- Oxygen toxicity - Contaminated air - Decompression sickness - Gas narcosis
What options can I choose from when selecting a dive log?
- Paper: - Range in size and information you record - Training dives and non-training dives - Electronic: - Click boxes with a few type in fields - Some dive computers will download dive data that you can upload into your elog
What are nine signs/symptoms of decompression sickness? How soon do they occur after a dive?
- Paralysis - Dizziness - Tingling - Joint and limb pain - Shock - Numbness - Difficulty breathing - Weakness and prolonged fatigue - Unconsciousness - There occur 15 minutes to 12 hours after a dive but can be after 12 hours
What role do I have as a diver in the long-term survival and health of the world's aquatic ecosystems?
- Part of the solution - Report your observations by taking part in environmental surveys and reporting online - Add your voice and votes to those of other dives - Take direct action - Underwater cleanups
Why can no dive computer or table guarantee that decompression sickness will never occur, even within its limits and how do I address this concern?
- People vary in their susceptibility to DCS no dive computer or dive table can guarantee DCS will never occur
What is no stop (no decompression) diving and what is no stop limit?
- Plan you dives so that you can swim directly to the surface without unacceptable risk of decompression sickness
How do dive tables address repetitive diving?
- RDP (Recreational dive planner) uses three tables: - Table 1- assigns a pressure group letter that represents residual nitrogen - Table 2- gives credit for nitrogen leaving during a surface interval - Take pressure group from table 1 and find a new pressure group based on a surface interval time - Table 3- provides reduced no stop time for a repetitive dive
How do I set up and activate my dive computer and what is the first step?
- Read the dive computer manual - Set up the following: - Time and date - Metric or imperial units - Ascent rate alarm - you usually leave this on - Max depth and time alarm - To activate, press a button or touch some contacts - Check time and date after activation - Be sure there isn't a low battery warning
What is the difference between a decompression stop and a safety stop?
- Safety stop is not needed to be within the limits of most decompression models as a conservative measure to remain well within limits - Safety stops are required any time you come up to or within three pressure groups of a no stop limit and for any dive to 30m/100 ft or greater
What should I do if my dive computer fails during a dive or between dives?
- Signal your buddy to ascend, make a safety stop and end the dive - Wait 12 or more hrs to dive again - Continue the dive using your backup computer - Dive with both computers at all times
What options can I choose from when selecting dive lights?
- Size and brightness - Compact lights- stow easily - Not very bright better for day use - Larger lights - Righter and cover wider area - Specialized lights - Technical diving and underwater video - Power Source - Rechargeable battery - Disposable battery - Accessories - Clip to secure it when not in use - Wrist lanyard
What options can I choose from when choosing slates and wet books?
- Slate: - Rigid plastic that you write on a with an attached pencil or marker - Advantage - you can erase - Wet book: - Compact notebook with waterproof pages that you write on with a pencil - You don't reuse the pages - Advantage- more writing space
What items might I have in a spare parts kits?
- Spare mask strap, fin strap and snorkel keeper - Harness and weight belt buckle - Cable (pull) ties - Tools: wrench or spanner, pliers, screw drivers, hex wrenches or a scuba tool - Regulator mouth piece - Accessory clip - Slate or wet book pencil - Various sized cylinder valve o-rings - Cement or glue - Sunscreen and spare sunglasses
What happens to my no stop limits as I ascend to a shallower depth during a dive?
- The no stop time increases
Why is it important to be trained as a PADI Enriched Air Diver, or under the supervision of a PADI Enriched Air Instructor, before attempting to dive with enriched air?
- To avoid equipment related concerns associated with the higher oxygen content
How do I keep my dive skills and knowledge current and refreshed?
- Use them often by diving regularly
How often is it recommended that I have a complete physical examination for diving?
- When you start diving and regularly thereafter
How does a dive computer or dive table estimate the amount of nitrogen I absorb during a dive?
- Work by using dive time and depth information to calculate theoretical nitrogen in your body - Calculated estimates compared against limits from experimental dives and human experience
Why is it important to have a spare parts kit?
- You cannot dive if something is broken or missing
What do I have to do if I exceed a no stop limit?
- You must make an emergency decompression stops - Stops at specific depths for prescribed time to allow your body to release dissolved nitrogen - Emergency procedure only
How does my dive computer calculate repetitive dives?
- Your dive computer continues to calculate after a dive it remembers your residual nitrogen - It calculates your time and how much theoretical nitrogen dissolves out of body - Scroll your no stop limits as you relax during a surface interval, you'll see them gradually lengthen - On the next dive the computer knows residual nitrogen and shortens no stop times
Why is it important that I dive with the same computer on every dive I make on a given day and not turn my computer off between dives?
- Your dive computer tracks your personal theoretical nitrogen levels continuously during all your dive - If you use a difference computer, your no stop times would be inaccurate- significantly increases the risk of DCS - Do not turn off computer because all your data could be lost