Dive Tables Planning dives safely

Objectives Describe the function of the dive tables. Define common dive tables terminology and concepts. Plan repetitive dives not requiring stage decompression. Determine contingency mandatory decompression stops.

Main points Dive tables aid in planning safe dives by setting depth and time limits Must understand the terminology Must adhere to the rules Recreational diving does not involve decompression stops Decompression stops are listed for contingences purposes We utilize computer but understand the tables are still key to safe diving

Terminology Dive Profile Actual Dive Time (ADT) Depth or max depth statement of depth and time 70 feet for 40 minutes Actual Dive Time (ADT) Surface to surface time Depth or max depth Deepest point of dive no matter how brief the time spent there. Maximum Dive Time (MDT) Maximum time you can spend on a dive to a given depth without requiring a mandatory decompression stop.

Terminology End-of-Dive Letter Group Surface Interval (SIT) New Group Symbol representing amount of excess nitrogen in your body at the end of the dive. Surface Interval (SIT) Time on surface between dives. During the SIT you are getting rid of some excess nitrogen (off-gassing) and therefore your letter group, will change. New Group Letter group at the end of the SIT Repetitive Dive Any dive made within 24 hours of a preceding dive.

Terminology Residual Nitrogen Time (RNT) Adjusted Maximum Dive Time Excess Nitrogen in your body after a dive Represented by your new group at the end of the SIT Adjusted Maximum Dive Time The maximum dive time for a repetitive dive to a given depth. Total Nitrogen Time (TNT) Represents total nitrogen load in your body at the end of a dive Determined by combining RNT +ADT = TNT

Terminology Safety Stop Mandatory Decompression Stop (Deco stop) Voluntary stop at the end of every dive Facilitates outgassing of Nitrogen Reduces the likelihood of bubble formation Mandatory Decompression Stop (Deco stop) Required stop at 15 feet whenever MDT or AMDT has been exceeded Beyond the training of recreational diving

Rules for Using the NAUI Tables Rate of ascent 1/2 foot per second or slower. Depth Use exact or next greatest number. Time Use exact or next greatest number Dive sequence Deep to shallow recommended During the dive For any rep. dive SIT Minimum recommended : 1hr Minimum recognized : 10min Keep activity to a minimum Drink water

Rules for Using the NAUI Tables Sport Diving Maximum Depth 130ft Altitude Diving Special training/tables required when diving at altitudes above 1000 feet. Flying after diving 1 recreational dive: 12 hours Multiple recreational dives: 18hrs Multiple dive/multiple days: 24hrs Mandatory deco stop: 24hrs Long, cold, strenuous dive Use next greater TNT

Safety stops Maintain depth of 15ft for 3mins Minimal activity throughout the stop. Deep stops: (different schools of thought) initial 1-minute stop at a depth equal to ½ the Max depth, followed by a 3-minute stop at a depth of 15 feet. For example, on a dive to 100 feet of seawater (FSW), make a 1-minute stop at a depth of approximately 50 feet, followed by 3-minute stop at a depth of approximately 15 feet.

Stage Decompression Diving Dives that require a mandatory decompression stop. Beyond the realm of sport diving However you should have contingency information and be familiar with the minimal emergency procedures in case the maximum recreational dive time is exceeded. Omitted Decompression Missed mandatory decompression stop and no symptoms Rest, drink fluids, and watch for signs of DCS. Do not re-enter water for at least 24 hours. If signs/symptoms of DCS are present treat for DCS

Walking through the table Find depth column Find dive time rows Find max time for 40ft, 60ft, 100ft Find max time for 44ft, 55ft, 81ft Finding letter groups 60ft/30min 70ft/36mins 81ft/22mins

Table 2 (SIT Times) Finding your next letter group Letter group E SIT for 1hr SIT for 1hr 20mins SIT for 2hrs Letter group H SIT for 30mins SIT for 1hr 8mins 3hrs

Table 3: Repetitive dive table Starting off with a new letter group Find your planned Max Depth Top number is your RNT Bottom number is your AMDT Examples E diver: what's your AMDT for 40ft 60ft 75ft

Lets get complicated Dive 1 Dive 2 60ft/40mins Letter group? 2hr SIT New letter group? Dive 2 MDT for 50ft? SIT time for a 30min dive at 50ft? If SIT=2hrs; then dive = 50ft/30mins what’s my new letter group? (TNT calculation)

Mandatory Decompression Stops Found in table 1 Boxes to the right of the circled numbers Top number Indicates ADT requiring Mandatory Deco stoop Bottom number # minutes that must be spent at 15 feet Example A diver has a dive schedule of 100 feet/23 minutes The diver must spend 5 minutes at 15 feet Note that any time from 22:01 – 25:00 requires this stop

Mandatory Decompression Stops The actual stage decompression tables for air diving are extensive. The information provided here is for contingency purposes only. Stage decompression diving requires extensive training and equipment, and is beyond the realm of recreational diving.

Before the Dive Prior to entering the water for any dive you must ask yourself, and answer, the following questions: How much excess Nitrogen, if any, do I have left in my body from previous dives? Residual Nitrogen Time or RNT What will be the maximum depth of my dive? What is my time limit for the planned depth of the dive?

Post Dive After the dive you must ask yourself, and answer, the following questions: What was the maximum depth of my dive? How long did I stay under water? Actual Dive Time (ADT). What is the total Nitrogen load in my body? Total Nitrogen Time (TNT). What is my end of dive letter group?