Questions like this can catch you out if you've been focusing on the partial pressure of the gas; converting the physical amount into its physiological effect when breathed by a diver at pressure.

The question is asking what the physical amount is in the cylinder. This will not change with the change in pressure.1% in the cylinder at the surface will still be 1% in the cylinder at 30m/sw.

Want to learn more about physics in diving? Join one of my upcoming PADI Professional Development Programs - the PADI Divemaster or the PADI Instructor Course.

The PADIEmergancy Oxygen Provider Course may be taught to anyone of any age, with an interest. As a non-diving program, there is no diving prerequisite, much like the EFR programs, and may be used in non-diving situations.

As with the EFR programs, consideration should be taken when admitting children on the course.

Want to become a PADI Emergency Oxygen Provider Specialty Instructor? Book Now and Ignite YourLife today!

Time to break out the PADI RDP (or even the PADI eRDPml), everyone!

22m for 35 min should leave you PG-R.

SI for 45 mins then takes us to PG-I.

Flip over to Table 3 and intersect I with 16 metres. 

You'll see the white box indicates the RNT will be 29 mins and now it's time for the A.R.T. of dive planning!

A=Actual Bottom Time - 36 mins

R=Residual Nitrogen Time - 29

T=Total Bottom Time 36+29=65 minutes.

Visible light is electromagnetic energy and depending on how far the light has to travel through a liquid will determine what parts of the wavelength we can see. 

This means the deeper or murkyer the water we're diving in will determine what colours we can see. 

All gases will affect us differently when breathed under pressure and Helium, commonly used in deep Trimix dives, is no different.

Manifestations such as tremors, headaches and involuntary twitching can occur but this reserved for depths of approximately 100m/sw or deeper.