RMV from a dive answers how much gas do I really breathe? Give it the gauge readings, time and average depth of one stretch of a real dive and it returns your respiratory minute volume (RMV): the gas you breathe per minute, brought back to surface pressure so it holds at any depth.

What you enter

• Size, each (L): the water capacity of one cylinder.
• Cylinders: Single, or Twin for doubles or sidemount. Twin counts both at the same pressure.
• Start and End (bar): the gauge at the beginning and end of the stretch. End must be lower than Start.
• Time (min): how long the stretch lasted.
• Average depth (m): the average over the same stretch, from your dive computer’s log.
• Water: Salt or Fresh.

This tool keeps its own cylinder, so you can measure on a different set from the one the other tools use. Water is shared with them.

Reading the result

• RMV (L/min): the main figure, surface-equivalent.
• SAC (bar/min): the same rate as gauge pressure, true only for this cylinder.
• Gas breathed (L): the free gas the pressure drop represents.
• Ambient (bar): the pressure at the average depth.

The verdict states what you breathed, for example You breathed 1200 L of gas in 30 minutes at 15 m. The RMV is worked out so that it does not under-predict that gas use, whether you use it in these tools or in the planner.

Under the figures, a button labelled with the figure, such as Use 16 L/min, sends the RMV, to the nearest half litre, to Gas needed, Turn pressure and Minimum gas. The button then reads In use, and their Breathing group notes that the figure was measured. Typing a new RMV in any of them replaces it.

Measuring a figure you can plan with

• Choose a steady stretch. Leave out the descent and a busy ascent; they are not the rate you hold at depth.
• This is a relaxed rate. A problem at depth raises it sharply, which is why Minimum gas multiplies it by a stress factor.

Next

• Gas needed uses the figure for a dive.
• Breathing rates is where a plan takes its RMV.