Nitrox

Question 1

The primary benefit of using enriched air nitrox is that it

Answer 1

Gives you longer no stop times compared to air

Question 2

When using EANx, you should expect narcosis to be

Answer 2

No different than diving with air

Question 3

The primary concern regarding enriched air nitrox and equipment is high oxygen content.

Answer 3

because some materials more readily burn, or even explode, in the presence of oxygen.

Question 4

The recommendations for using equipment, other than cylinders, with enriched air with up to 40% oxygen, include that (choose all that apply)

Answer 4

Generally, for all equipment except your cylinder you can use regular scuba equipment with enriched air with up to 40% oxygen.

However, local laws, standards or practices may require special fittings or cleanings; follow these if they apply.

In any case, during servicing, oxygen compatible lubricants, as well as other materials, are generally recommended.

Question 5

The potential hazards of improper enriched air filling procedures include (choose all that apply)

Answer 5

Fire or explosion

Making the percentage of oxygen blend questionable

Question 6

The markings that, according to broadly accepted dive community practices, you should have on a scuba cylinder used for enriched air nitrox include

Answer 6

The minimum markings on an enriched air cylinder include all the markings required of an air cylinder, plus a band around the cylinder shoulder reading NITROX, ENRICHED AIR or the like.

Yellow cylinders should have a 10 centimetre/4 inch green band.

Non yellow cylinders should have a 15 centimetre/6 inch band. The top and bottom of this band should be a yellow, 2.5 cm/1 in. band, with the center 10 cm/4 in of green.

There should also be a sticker/decal indicating whether or not the cylinder is oxygen service rated, and a tag or sticker with the diver’s name, the EANx blend, fill date and the maximum depth for using the blend.

Local laws or standards may also add or substitute required markings. The blender’s name, initials or the boat name may be on the cylinder, but these are not considered required markings.

Question 7

The maximum oxygen partial pressure is _____________ and contingency partial pressure is ________________.

Answer 7

The maximum oxygen partial pressure for a given blend is 1.4 ata/bar. The contingency maximum is 1.6 ata/bar.

The higher the oxygen content, the shallower the depth at which you reach 1.4 ata/bar.

Question 8

The primary hazard of exceeding oxygen limits is having a _________________ which is likely to lead to ______________ underwater

Answer 8

The primary hazard of exceeding oxygen limits is having a CNS (central nervous system) convulsion. The convulsion is not usually fatal itself, but if it happens underwater, is likely to lead to drowning.

Question 9

To avoid the primary hazard of exceeding oxygen exposure limits (choose all that apply)

Answer 9

Stay within the limits of your computer and stay shallower than the max depth of the blend

Question 10

Signs and symptoms always precede a CNS convulsion.

T/F

Answer 10

Signs and symptoms always precede a CNS convulsion.

Question 11

Signs and symptoms that indicate a diver may convulse due to oxygen toxicity include (choose all that apply)

Answer 11

VENTID – Visual disturbances; Ear ringing; Nausea; Twitching; Irritability; anxiety and euphoria; and Dizziness.

Question 12

When using an EANx compatible dive computer to manage oxygen, you should (choose all that apply)

Answer 12

Set the maximum oxygen partial pressure for 1.4 and set the computer for the blend you’re using.

Find the maximum depth. You should watch the depth as your primary means of staying shallower than this depth –

use the computer’s warning as a secondary alert.

Stay well within the computer’s oxygen exposure limits.

It’s generally recommended that you allow at least an hour between nitrox dives to help stay well within oxygen exposure limits.

Question 13

What should you do if you accidentally exceed the oxygen limits of your computer?

Answer 13

End the dive immediately. Ascend, make a safety stop and surface.

You should not dive for at least 24 hours, or for the minimum interval recommended by the computer manufacturer.

Question 14

Who must personally verify the oxygen analysis of a cylinder of enriched air?

Answer 14

The diver using the cylinder

Question 15

What is the first step you do when analyzing an enriched air blend?

Answer 15

1) Attach the analyzer to a flow restrictor or flow meter supplying air from a cylinder of air.

2) Calibrate the analyzer for 20.8% to 21% (depending upon the analyzer).

3) Attach the analyzer to a flow restrictor or flow meter supplying enriched air from the cylinder being analyzed.

4) Analyze the enriched air oxygen content.

5) Compare your analysis with the analysis on the contents sticker or tag.

6) Complete the fill log.

If you have any questions about these steps, review the section on analysis, or ask your PADI Instructor for more guidance and information.

Question 16

What should you do if your enriched air computer fails during a dive?

Answer 16

Immediately ascend, make safety stop and surface.

don’t dive again for at least 12 hours, or longer if specified by the computer manufacturer.

Question 17

If a diver convulses underwater, your priority is to get the diver to the surface. Treat the diver as an unresponsive diver.

T/F

Answer 17

T

Hold the mouthpiece in if it’s in the mouth, but don’t waste time trying to replace it if it’s not.

Take the victim to the surface, establish ample buoyancy, check for breathing and call for help.

Provide rescue breaths if the victim isn’t breathing.

Get the victim to the boat or shore and check for a pulse and breathing.

Provide CPR as necessary while waiting for EMS.

Some experts recommend that if the victim’s mouthpiece is in place, hold it there and wait for the convulsion to subside before surfacing the victim.

Question 18

If a diver is suspected of having decompression illness after an enriched air dive, the steps to take are (choose all that apply)

Answer 18

Provide emergency oxygen and first aid/CPR as necessary, and contact EMS, DAN and/or other appropriate emergency services for the area.

When possible, tell emergency personnel the particulars about the diver’s dive profile, including depth, time and whether the diver was using a dive computer or tables and what the blend was.

If you run out of oxygen before reaching emergency care, you can provide a breathing patient with enriched air available.