Kiss valves are gas flow orifices build by Jetsam in Canada. Kiss valves are the first used for sports diving. The principle was already used in several military rebreathers but became available around 2000 for the sport diving industry.

• orifice diameter = 0,004"

• orifice diameter = 0,1016 mm

• Can be used with IP pressures up to 10 bar

• The Teflon seal last almost a lifetime

• Oxygen flow is constant up to 40 meter (IP=10bar)

• Overhaul only by factory

• Push button to manual add oxygen, difficult to
  operate for some people

• orifice diameter = 0,0035"

• orifice diameter = 0,089 mm

• Can be used with IP pressures up to 12 bar

• O-ring seals, must be changed once a year

• Oxygen flow is constant up to 50 meter (IP=12bar)

• Overhaul by user very simple

• More easy adding oxygen manually

To calculate the oxygen flow through the orifice the formula D_n = d² x p₀ x A₁ can be used. More details see this page. So to calculate the flow through the Kiss valves following is known: A = 8,65 for pure oxygen. 

The flow through the old KISS style valve is calculated in this way:

Dn = (0,1016mm)² x 8,65 x 10 bar = 0,893 ltr/min.( @ 10 bar depth=40mtr)

The flow through the new KISS style valve is calculated in this way:

Dn = (0,089mm)² x 8,65 x 12 bar = 0,822 ltr/min.
( @ 12 bar depth=50mtr)

Dn = (0,089mm)² x 8,65 x 10 bar = 0,69 ltr/min.
( @ 10 bar depth=40mtr)

It must be mentioned that deeper dives can be made, but the oxygen flow will decrease when the depth belonging to half the intermediate pressure is reached. Manual addition of oxygen must be applied more often, until a depth of the (IP - 1 bar x 10) is reached, there the flow will completely stop.
For those who wish to go deeper, the orifice of the New version valve can be removed and the hole plugged.  If it is plugged there will be NO constant flow of oxygen.  Adding oxygen manually will be the ONLY way to get O2 into the system. 

I want to thank Kim and Gordon Smith for there kind cooperation !

***It was very sad news Gordon Smith passed away January 2006.
Thanks for all you did for us! Kim, I wish you all strength***