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