Hi
@stuartv
Over the years, I have struggled with trying to understand the ANSTI simulator testing of regulators. Some background for the testing equipment can be found at
Ansti Test Systems Ltd under products/Life Support Equipment Test Facility.
The graphics results in the recent Scuba Diving article are mislabeled and make it harder to understand. The first parameter listed should be RMV rather than BPM, i.e. 37.5 RMV. The breathing rates used are actually 15, 30, and 25 breaths/min @ 2.5 liters per breath. This generates the RMVs of 37.5, 75, and 62.5 liters per minute, corresponding to 1.32, 2.65, and 2.21 cubic feet per minute.
The 4 standard testing conditions are:
1) 15 BPM, RMV 37.5, 132 fsw/5 atm. This is said to be an aggressive breathing rate at the recreational limit. To put this into perspective for me, this is more than 3.5 times my average RMV and more than twice the highest RMV I have ever had on a complete dive. I have no good idea of the highest instantaneous rates I have achieved on my most strenuous dives.
2) 30 BPM, RMV 75, 132 fsw/5 atm. This is said to be the rate for a single diver at an extremely heavy work load and to simulate 2 divers breathing at an aggressive rate. It is twice the rate in #1, a lot of breathing.
3) 25 BPM, RMV 62.5, 165 fsw/6 atm. This is the European conformance standard EN250
4) 25 BPM, RMV 62.5, 198 fsw/7 atm. This is the US Navy Class A test. The ScubaLab test uses a high pressure supply of 725-760 psi, apparently, the Navy uses a higher pressure that may improve some regulator performance.
Each regulator is rated excellent, very good, good, or fair as outlined by
@tbone1004 in post #9. If the inhalation or exhalation resistance exceeds 25 millibars, the test is discontinued and the result is listed as N/A, there are several examples in the results.
So, do I think this testing has a real world correlate? Maybe
. Obviously, it depends on the depth of your dives and your RMVs. I mainly dive within recreational limits. Only 1% of my dives have been deeper than 130 feet, with a deepest of 161 feet. I have a reasonably low average RMV with a relatively narrow range. It is not very likely that I am going to push my regulator into the ranges represented by the more strenuous testing conditions, but it is possible. Personally, I'm glad to have the leeway provided by a higher performing regulator, currently a Scubapro Mk25/S600. Looking at your own dive depths and RMVs will give you a rough idea of how the testing results may apply to you.
Again, for perspective, the Innovative Scuba Concepts Honu was the "worst" performing regulator. It was rated very good in ANSTI test #1 but did not complete testing under the other 3 conditions. However, divers rated it very good for ease of breathing in all positions except face-up (looking up), where they rated it good. There you go.
Under the most usual circumstances (within recreational depth limits and a normal range of exertion), nearly any regulator should perform acceptably. At deeper depths and with extraordinary exertion, a higher performing regulator may prove superior. I'd be most interested in hearing from divers with dives meeting these conditions.
Good diving,
Craig