Nitrox certification

Why may you need additional thermal protection for Nitrox diving?

Whether you dive in the tropics or in colder waters, the extended bottom times provided by Nitrox will usually necessitate more thermal protection/insulation than you might ordinarily wear

Decompression diving involves more risk than no-decompression diving, and without the proper precautions can become extremely hazardous.

true

It is important for team members to be use the same Nitrox mixture so that they will share a common MOD.

true

Your signature in the gas fill log indicates:That you take responsibility for the Nitrox that has been delivered to you, and that you are satisfied that your cylinders have been filled properly.

true

What is the key reason why, when available, technical divers generally prefer Trimix for dives past 40 m/132 ft?

The concept behind Trimix diving is that by replacing most of the nitrogen in the breathing gas with helium, you will be affected less by nitrogen narcosis than you would be using regular air.

The MOD for EAN32 is 30 m/99 ft.

False

The primary risk associated with Nitrox diving (as opposed to diving air) is carbon monoxide (CO) poisoning.

False

To qualify as Nitrox, a gas mixture must generally contain at least 32 percent oxygen.

False

You ask a Nitrox blender to fill your cylinders with EAN30, but they analyze at 32 percent. You should not be concerned, as this is within the acceptable range of accuracy for Nitrox fills.

False

What are the primary component gasses found in air, and the percentage of the total gas mixture each gas represents?

- However, unlike air which normally contains approximately 79 percent nitrogen and 21 percent oxygen, Nitrox contains a higher percentage of oxygen.

State how long, in any 24-hour period, you can be exposed to a Nitrox mixture at its Maximum Operating Depth (MOD)?

-Also, over the course of a 24-hour period, you will have a cumulative time limit for oxygen exposure at the maximum operating depth of two and a half hours in any 24-hour period.

What are four additional steps divers can take to help avoid oxygen toxicity while using Nitrox?

-Analyze and label every cylinder prior to diving. -Set the appropriate mix in your dive computer and do not exceed the limitations it gives you during the dive. -Never exceed a PO2 of 1.6.

What are four things divers can do to help minimize the general risks associated with Nitrox and other forms of diving?

-Avoid overheating. -Wear adequate thermal protection while diving in cold water. -Never dive with Nitrox deeper than the MOD for the mix you are using. -Avoid heavy exercise while diving with Nitrox. -Get medical clearance for diving if you are an insulin dependent diabetic and if cleared to dive, restrict your diving to shallower depths. -Get medical clearance for diving if you are taking any of the other drugs listed in this chapter. If cleared to dive, restrict your diving to shallower depths.

What do divers commonly call a person who creates the Nitrox used to fill scuba cylinders?

-Blender

What is the primary cause of decompression sickness?

-Decompression sickness usually occurs when you have an excess amount of nitrogen in your body and you ascend too quickly. The nitrogen comes out of a solution and forms a bubble thus disrupting the flow of blood in whatever part of the body it is located.

What does the term decompression stop mean?

-During these decompression stops, the excess nitrogen in your body is carried back to the lungs where you exhale it each time you breathe.

What are two reasons why EAN32 is a good choice for Nitrox diving?

-EAN32 will provide you with a good combination of extended bottom time and unrestricted depth within the sport diving range. In addition, using EAN32 poses less risk in terms of exposure to oxygen than other richer mixtures. You'll learn more about the risks in Nitrox diving in the next chapter.

What is the recommended first aid for decompression sickness?

-First aid for decompression sickness includes treating the diver for shock by laying them down and keeping them either from being to cold or too warm. However the most important thing to do is provide an injured diver pure oxygen as soon as possible and transport to a hyperbaric chamber where proper recompression therapy can be performed.

What may happen if you go too deep or stay too long during a dive?

-However, if your dive lasted for a long time, or you made a deep dive, the dive computer will indicate that you must stop at a particular depth to allow the excess nitrogen in your body time to escape without causing problems. Your computer may require you to make one stop or a series of stops, commonly known as decompression stops.

What are the common terms divers may use when referring to Nitrox?

-In all likelihood, you have also heard it referred to by a variety of names: enriched air, oxygen enriched air, SafeAir®, Denitrogenated Air®, EAN, EANx, NOAA Nitrox I or NOAA Nitrox II.

What does term Nitrox mean?

-Nitrox a mix of nitrogen and oxygen just like air.

What does the term oxygen toxicity mean?

-Oxygen toxicity (also referred to as oxygen poisoning) is a physiological reaction of your body that occurs when you are exposed to breathing mixtures containing high partial pressures of oxygen, or mixtures containing lower partial pressures of oxygen for extended periods. It can be more easily understood as a condition that occurs when the diver breathes a mixture of gas that allows the PO2 to exceed 1.6 by going to deep or exceeding the time limit at a lower PO2. Therefore you as a diver must set and follow your MOD for every mix on every dive. -Pulmonary Oxygen Toxicity can develop when you are exposed to elevated levels of oxygen over long periods of time. However the length of time involved is well beyond that of most recreational dives. Thus it poses no real risk to sport divers. -Central Nervous System (CNS) Oxygen Toxicity is of greater concern. This is because all a diver must do is violate the Maximum Operating Depth (MOD) for a particular mix causing the P02 to rise above 1.6 and the chances for a CNS hit increase exponentially.

What are the two primary benefits divers enjoy by using Nitrox?

-The first is that you can increase your maximum allowable bottom time. This happens because the extra oxygen added to your breathing gas when it was filled has displaced nitrogen. Because there is less nitrogen in the mix to be absorbed by your body you can spend longer at depth before you reach the nitrogen limit - which is the decompression limit. -Secondly, since you are absorbing less nitrogen on a given dive, your surface intervals can usually be shortened.

What does the term MOD mean? How is it used in Nitrox diving?

-The higher the percentage of oxygen used in the mixture, the shallower the Maximum Operating Depth or MOD is for a particular mixture. -shallower depth, planned diving, longer time

What are the most common symptoms of decompression sickness?

-The most common symptoms include, but are not limited to, pain in the joints, numbness, paralysis, loss of balance, muscle weakness, and impaired thinking.

How can a dive computer help you avoid decompression sickness?

-When you use a dive computer, it will calculate approximately the amount of nitrogen absorbed by your body, and indicates when it is time to ascend and the rate at which it is safest to ascend.

What is the primary risk associated with Nitrox diving?

-inc oxygen exposure -sickness/poisening

What are three reasons why sport divers should avoid decompression diving?

-sport divers should avoid decompression diving by using their dive computers to plan their dives, and carefully monitoring their computers during dives.

What is the maximum partial pressure of oxygen (PO2) we use in Nitrox diving?

1.6

What is the recommended surface interval after extended dives with Nitrox?

120 min

During any 24-hour period, you can be exposed to a Nitrox mixture at its Maximum Operating Depth (MOD) for up to:

150 Min

What is the minimum concentration of oxygen required to maintain consciousness at sea level?

16%

What are some of the common Nitrox mixtures used by divers?

22-40 percent mixture -EAN32: 68 percent nitrogen, 32 percent oxygen. -EAN36: 64 percent nitrogen, 36 percent oxygen.

What are the minimum and preferred surface intervals for Nitrox diving?

30 min,60 preferred

The maximum percentage of oxygen that sport divers use in a Nitrox mixture is:

40%

What is an oxygen analyzer?

An electronic device used to measure the percentage of oxygen in a gas mixture.

What are the two most important pieces of information that will appear on a Nitrox fill tag or label?

Any tank used for Nitrox diving must also have a tag or label attached to it where the exact Nitrox mixture used in the tank (FO2) and its MOD can be read

What are two equipment items that do not need to be cleaned for oxygen service?

BC+Dry suit valves

What are the words represented by the acronym CONVENTID?

CON: The CON stands for convulsions, the most dangerous and potentially fatal risk in using Nitrox. The convulsions that occur during oxygen poisoning are similar to an epileptic seizure and may occur without warning. When a convulsion occurs underwater, drowning and death frequently occur. The remaining symptoms may or may not occur prior to a convulsion. V: The V in CONVENTID stands for visual disturbances, which may take the form of tunnel vision or the perception of bright flashes of light when nothing is there. E: The E stands for ringing in the ears and other auditory hallucinations. N: The second N stands for nausea. Vomiting underwater is distinctly unpleasant and dangerous. T: The T represents twitching of the muscles, particularly the cheek, nose or eyelids. I: The I indicates irritability or apprehension. D: The D stands for dizziness.

Dive computers work by:

Calculating the approximate amount of excess nitrogen present in your body, based on factors such as depth and time.

What is the most important setting that must be made to your Nitrox computer before every dive?

FO2

What is the maximum recommended depth for using 100 percent oxygen?

During World War II, military divers found that they could dive with 100 percent oxygen, but only use this mixture down to a depth of 6 m/20 ft

Which of the following is another term divers commonly use when referring to Nitrox?

Enriched air nitrox

What are two equipment items that do not need to be cleaned for oxygen service?

Equipment that is exposed to low pressure oxygen, such as buoyancy compensators and their low pressure inflators and dry suit inflation valves do not need to be cleaned or lubricated for oxygen service.

What are the two most important pieces of information that will appear on a Nitrox fill tag or label?

Fo2 + MOD

Oxygen toxicity is a physiological reaction of your body that occurs when you are exposed to breathing mixtures containing:

High partial pressures of oxygen, Lower partial pressures of oxygen for extended periods

What are eight factors that may increase a divers susceptibility to oxygen toxicity?

If you overheat during a dive. If you are an insulin dependent diabetic. If you suffer from a deficiency of Vitamin E. If you have an overactive thyroid (hyperthyroid) gland. If you dive without proper thermal protection in cold water. If you use drugs that may speed the onset of oxygen toxicity, such as adrenocortical hormones, dextroamphetamine, epinephrine, norepinephrine, and paraquat. If you make a dive in which you are working or swimming hard underwater. If you have scar tissue in your lungs you may be more susceptible to oxygen poisoning.

What is the FO2 setting most dive computers default to?

In most cases, the default setting for the percentage of oxygen will be 21 percent. The default setting for PO2 is frequently 1.4. If you fail to change these settings you will not be getting the full benefit of the capabilities of your computer and Nitrox.

What is the most important setting that must be made to your Nitrox computer before every dive?

Most modern Nitrox dive computers allow you to set the percentage of oxygen in your breathing mix anywhere between 21 percent and 50 percent oxygen. A few will even allow richer mixtures. However, most require that the percentage of oxygen in the mixture be set before you enter the water. This procedure must be done prior to the start of every dive.

Additional steps Nitrox divers can take to help avoid oxygen toxicity include all of the following except:

Never exceed a PO2 of 2.0.

The air we normally breathe consists primarily of:

Nitrogen + Oxygen

What are the two gases that most Nitrox diving computers take into consideration when computing your allowable bottom time?

Nitrogen and oxygen.

Decompression sickness usually occurs when you have an excess amount of __________ in your body and you ________ too quickly.

Nitrogen, asend

What is the minimum concentration of oxygen required to maintain consciousness at sea level?

On the surface, you can breathe gas mixtures containing as little as 16 percent oxygen and still maintain consciousness.

What is an oxygen analyzer?

Oxygen analyzers are electronic devices that are used to measure the percentage of oxygen in a gas mixture. They run on batteries and most are equipped with a sensor that measures the percentage of oxygen in a gas mixture.

Which of the following statements best describes a decompression stop?

Pausing at a fixed depth for a specified period of time to allow excess nitrogen to exit your body more slowly.

What does the term technical diving refer to?

Technical diving is a type of recreational diving that goes beyond sport diving limits. Typically, it requires additional specialized training, planning techniques, and equipment. It provides the diver with capabilities well beyond the limitations of sport diving.

What does the term EAN32 mean?

That mixture is 68 percent nitrogen and 32 percent oxygen (EAN32).

What does a Nitrox tank wrap used to identify Nitrox cylinders look like?

The industry standard for tanks filled with Nitrox is to mark the tank with both a tank wrap, as well as to identify the mixture with a label or tag. A Nitrox tank wrap is an adhesive decal, generally 10-13 cm/4-5 in in width, that is designed to completely encircle the diameter of the tank. The tape is usually printed in yellow with bold green letters with the words Enriched Air and/or Nitrox printed continuously on it. This tape makes it quick and easy to spot a Nitrox bottle in a group of tanks.

The term Maximum Operating Depth (MOD) refers to:

The maximum depth a Nitrox Diver can reach without exceeding the limits of the oxygen concentration in the Nitrox mixture he is using.

What is the MOD for EAN32?

The reason EAN32 is considered the optimum Nitrox mixture is because it is the most oxygen rich mixture that you can use up to the maximum recommended sport diving depth limit of 40 m/132 ft.

What are the key difference between semi-closed circuit and fully-closed circuit rebreathers?

The semi-closed circuit rebreather is designed to re-circulate most of each breath you take, by removing the carbon dioxide (CO2) from your exhaled breath and adding oxygen as it is consumed. fully-closed circuit models do not release any breathing gas bubbles into the water, except during the ascent at the end of the dive. They work in a similar manner to the semi-closed circuit rebreather.

Why may you need additional thermal protection for Nitrox diving?

To compensate for heat loss on longer dives.

What of the following best describes the blender's job?

To supply you with the gas that you ask for when you present your cylinder to be filled.

What does the term blender mean, as it applies to Nitrox diving?

To the Nitrox diver, the blender is an important person who holds the key to your Nitrox diving. Without a properly trained blender, you wont be able to dive Nitrox with any degree of confidence.

First aid for decompression sickness can include:

Treating for shock., Administering pure oxygen.

EAN32 is a good choice for Nitrox diving because it provides a good combination of safety and extended bottom time.

True

If you go too deep or stay too long, you may not be able to make a direct ascent to the surface without substantially increasing your risk of decompression sickness.

True

Once a diver suspected of suffering from decompression has been transported to a medical facility, proper treatment will primarily involve recompression in a hyperbaric chamber.

True

Regulators that will be exposed to oxygen concentrations of less than 40 percent need no special preparation unless required by manufacturer's specifications or local laws/regulations.

True

The maximum recommended depth for using 100 percent oxygen is 6 m/20 ft.

True

The minimum surface interval for Nitrox diving is 30 minutes; however, 60 minutes is preferred.

True

The most common symptoms of decompression sickness can include, but are not limited to, pain in the joints, numbness, paralysis, loss of balance, muscle weakness, and impaired thinking.

True

The primary benefits of using Nitrox include longer bottom times and shorter surface intervals.

True

Your SDI Nitrox Diver certification allows you to use Nitrox mixtures whose oxygen content ranges as high as 40 percent (EAN40)?

True

The V in the acronym CONVENTID stands for:

Visual distortion.

Which of the following is not a factor that may increase a diver's susceptibility to oxygen toxicity?

Vitamin C deficiency.

A mixture of nitrogen and oxygen in which the percentage of oxygen is greater than that found in air is generally called:

all

The steps to follow when analyzing Nitrox cylinder content include:

all

Which of the following are things divers can do to help minimize the general risks associated with Nitrox and other forms of diving?

all

Which of the following best describes a Nitrox tank wrap?

all

f you do not set your dive computer's FO2 prior to every dive:

all

What are the changes that must be made to a regulator to prepare it for use with Nitrox mixtures whose FO2 does not exceed 40 percent?

and Nitrox regulators use special o-rings and other Nitrox compatible components including lubricants. The real value of a dedicated Nitrox regulator is in situations where levels of oxygen higher than 40 percent will be used. markings are yellow and green

What are the steps to follow when analyzing Nitrox cylinder content?

calibrate, analyze, label Begin by connecting your analyzer system to its calibration source, be that a cylinder of pure oxygen, premixed Nitrox or air. Oxygen sensors are not only sensitive to oxygen, they can also be affected by the presence of moisture, changes in temperature, sensor age and other factors. Therefore, every time you use an oxygen analyzer, you must calibrate its display against a reference gas whose FO2 is unequivocal. This can be pure air, oxygen or, lacking these a Nitrox mixture with an FO2 that has been verified by at least two other analyzers. Most Nitrox divers use pure air as a reference gas, as its FO2 is unequivocal and, being closer to the FO2 of the mixture being analyzed, the margin for error is less than it would be if using pure oxygen as a reference gas. Turn the calibration source on. If using an oxygen regulator or other means of adjusting gas flow, adjust the flow rate to that specified by the analyzer manufacturer. Fixed rate meters generally restrict gas flow to a rate of approximately two litres per minute; this is an acceptable rate for most analyzers. Once the gas is flowing, and has had the opportunity to displace the air previously in the line, adjust the calibration dial so that it reads either 100.0 percent for oxygen, 20.9 percent for air or the correct percentage for another calibration source, if used. (The calibration dial may be very sensitive; getting the setting within +/- 0.1 percent of the target is generally considered adequate.) Allow the calibration gas to flow for at least another 30 seconds. Make certain there are no substantial variations in the FO2 reading during this time. If you will be analyzing several cylinders in succession, you only need to calibrate your analyzer once. Disconnect the analyzer set-up from the calibration source. Reconnect it to the cylinder you will be analyzing. Allow gas to flow until the analyzer reading stabilizes (this may take a while). Continue to allow gas to flow for another 30 seconds to ensure this reading remains constant. Disconnect and store your analyzer in a safe place. Remember to seal the O2 sensor, if separate, in a plastic bag, to protect it from moisture. Oxygen analyzers are delicate instruments and careless handling can damage them very quickly. To complete the process, mark the cylinder contents label with date, FO2, MOD, Limiting PO2, dive operation name and the name or initials of the person conducting the analysis.

The term blender refers to an individual who is qualified to:

create the Nitrox used to fill scuba cylinders.

Nitrox is still relatively rare at most dive destinations and liveaboards.

false

The term EAN32 refers to a Nitrox mixture:

n which the Fraction of Oxygen (FO2) is 32 percent.

The maximum partial pressure of oxygen (PO2) we use in Nitrox diving is:

none

What is the maximum percentage of oxygen that sport divers use in a Nitrox mixture?

or sport diving, we limit the range of Nitrox mixtures of up to EAN40 that work within the range of sport diving depths

What is the acceptable range of accuracy blenders must adhere to when asked to supply a Nitrox mixture with a particular FO2?

within 1 percent

What are the two gases that most Nitrox diving computers take into consideration when computing your allowable bottom time?

you may hear people talk about CNS (Central Nervous System) oxygen limits, OTUs (Oxygen Tolerance Units), OLF (Oxygen Limit Fraction), OTLs (Oxygen Time Limits), or use other terminology. At Scuba Diving International we prefer to use the term Oxygen Time Limit when we are referring to the maximum exposure you can have to enriched oxygen mixtures underwater