Operating Instructions
Page 24
Doc. 15301-RevB (2023-11-24)
4. Safety and Decompression
Stops
Safety and decompression stops are pauses inserted
into the ascent to the surface in order to reduce the
risk of decompression illness (DCI)�
4.1. Safety Stops
A safety stop is an optional stop added to all dives
before surfacing� Safety stops can be set to fixed
times of 3, 4, or 5 minutes, set to adapt based on
dive conditions, or turned off completely� See Deco
Settings�
The Tern does not do “deep safety stops”� That is,
there are no extra stops added around 15m to 18m
(50ft to 60ft) when ascending from a no-deco dive�
Safety stops always behave as follows:
Safety Stop Required
Once the depth exceeds 11m
(35ft), a safety stop will be
required� An alert will occur
when in the safety stop depth
range, shallower than 6m (20ft)�
Automatic Countdown
Countdown begins once the depth
becomes shallower than 6m (20ft )�
Countdown will continue while the
depth remains in the range of
2�4m to 8�3m (7ft to 27ft)�
Countdown Paused
If the depth goes outside of the
range 2�4m to 8�3m (7ft to 27ft),
then the countdown pauses and the
remaining time displays in yellow�
Safety Stop Complete
When the countdown reaches zero,
the display changes to “Clear”
and you are now clear to ascend to
the surface�
Countdown Reset
The countdown will reset if the depth
once again exceeds 11m (35ft)�
No Lockout for omitting
There is no lock-out or other penalty for
omitting a safety stop as they are optional�
If you ascend to the surface before the safety
stop countdown finishes, the safety stop will
appear paused, but this will disappear once
the dive ends�
We recommend performing safety stops as
planned as they offer a reduction in risk of
DCI and take little time�
.0
0
ft
STOPWATCH
SURFACE
Deep
19:16
FD
CLEAR
SAFETY
ft
125
.
6
O2/He
21/00
PPO2
.21
TTS
OC
SURFACE
mh
3412
C
L
E
A
R
INFO
Safety Stop
35ft /11m
Safety Stop Required /
Countdown Reset
20ft /6m
Countdown Begins
27ft /8.3m
Countdown Paused
7ft /2.4m
Countdown Resumed
Countdown Paused
Counting
Paused
Safety Stop Thresholds - Not to scale
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