Table 1 Signs and symptoms of nitrogen narcosis at different depths [2,29]

0–10

1–2

0.79–1.58

Unnoticeable/minor symptoms such as subtle changes in behaviour

10–30

2–4

1.58–3.16

Mild impairment of unpractised tasks

Impaired reasoning

30–50

4–6

3.16–4.74

Delayed response to visual and auditory stimuli

Calculation errors and poor choices

Mild amnesia

Overconfidence, idea fixation and a sense of well-being

Laughter (chambers) or anxiety (cold water)

50–70

6–8

4.74–6.32

Impaired judgement and confusion

Hallucinations

Delay in response to signals, instructions and other stimuli

Uncontrolled laughter, hysteria (in chamber)

Feelings of terror (in some)

70–90

8–10

6.32–7.90

Mental confusion

Loss of memory

Stupefaction and loss of judgement

90+

10+

7.90+

Hallucinations, increased intensity of vision and hearing

Unconsciousness

Death