Name those seconds !

[Nemrod]

Nemrod, I bow to your superior knowledge with regards to the exhaust valve… I never knew the difference was that significant! I’ll keep on using my late style 1085 seconds, especially the 1980 vintage one I got NOS in the early ‘90s And just took to the Bahamas!

There is nothing wrong or dangerous about the later 1085s as pictured in the ad copy with the large valve, tee and plenum. The ones with the restrictive tee with the two screws and the tiny exhaust valve are dangerous IMO and it was not just my opinion as USD/AL quickly and quietly corrected the problem. I am pretty sure there was a letter concerning this issue as well. I was working as a shop boy by about 1969 and I remember seeing something to that affect about 1970. My imagination or not for the letter, it was known at the time and it was not just the USD seconds but a number of such like the Sportsways that not only had one tiny little valve but had two and not side by side but stacked! Good grief!

Exhaust effort for WOB is just as important as the others, cracking effort and Venturi assist. You cannot get O2 in if you cannot get CO2 out. Talk about causing a headache, yeah, they were "that" bad. And I am not enthralled with the 109 either, though adequate, it is just that, adequate. The tee and plenum are decent but the valve is still only 26mm. The 156 and the G250 and the later 1085s have 30mm valves and that 4mm difference is huge. Here is a 109 and a 156 (CE) compared, that is a big difference and it is certainly noticeable in use.



The 156 is primary and the 109 is secondary:

 

[Skip Y]

I dove a ScubaPro 108 today. The 109 is adjustable where the 108 is not. For me the 108 worked fine, as did the MK 7 "Honker"

 

[jadairiii]

Exhaust effort for WOB is just as important as the others, cracking effort and Venturi assist. You cannot get O2 in if you cannot get CO2 out. Talk about causing a headache, yeah, they were "that" bad.

Agreed. For whatever reason I have found I am extremely prone to CO2 headaches. Only 2 regulators I have used have never given me a headache, Apex TX50 and the Poseidon Odin. And my list of regulators run the gambit, from Sportways W200, Watergill, MR12III, G250, and Conshelf's, and a few others I cant remember.

 

[John C. Ratliff]

Agreed. For whatever reason I have found I am extremely prone to CO2 headaches. Only 2 regulators I have used have never given me a headache, Apex TX50 and the Poseidon Odin. And my list of regulators run the gambit, from Sportways W200, Watergill, MR12III, G250, and Conshelf's, and a few others I cant remember.

Okay, as one who has used these regulators, operationally in USAF Pararescue missions, I can say that I‘ve never had a problem because of the smaller exhaust. My second single hose regulator was a Voit 40 Fathom, which was a copy of the original Calypso regulator. In the USAF, we were issued the USD Calypso (second generation, with the neck strap and smaller exhaust), and used it on many missions, including rather vigorous dives.

The problem with the smaller exhaust was that these regulators could not pass the U.S. Naval Experimental Diving Unit evaluations, and therefore were not ”approved” for U.S. Navy use. You won’t see a Navy diver using an original Calypso, or second generation Calypso, as they were not issued until USD increased the size of the exhaust. But the USAF did not adhere to Navy requirements, and local purchased these early Calypso regulators as they were much better for our missions, using parascuba jumps, than were double hose regulators (USD Aquamaster or, for USAF ops, Mistral regulators). But the original USD Calypso took Hannes Keller to 1,000 feet in the 1960s (in a tragic dive that cost his dive buddy his life, but not due to the regulator, due to improper gas management).

By the way, if you want to use a regulator with the least exhaust resistance, get a Scubapro Pilot or A.I.R. 1 regulator. The entire LP diaphragm is the exhaust valve. I have both, and love diving both.

SeaRat

 

[John C. Ratliff]

There is nothing wrong or dangerous about the later 1085s as pictured in the ad copy with the large valve, tee and plenum. The ones with the restrictive tee with the two screws and the tiny exhaust valve are dangerous IMO and it was not just my opinion as USD/AL quickly and quietly corrected the problem. I am pretty sure there was a letter concerning this issue as well. I was working as a shop boy by about 1969 and I remember seeing something to that affect about 1970. My imagination or not for the letter, it was known at the time and it was not just the USD seconds but a number of such like the Sportsways that not only had one tiny little valve but had two and not side by side but stacked! Good grief!

Exhaust effort for WOB is just as important as the others, cracking effort and Venturi assist. You cannot get O2 in if you cannot get CO2 out. Talk about causing a headache, yeah, they were "that" bad. And I am not enthralled with the 109 either, though adequate, it is just that, adequate. The tee and plenum are decent but the valve is still only 26mm. The 156 and the G250 and the later 1085s have 30mm valves and that 4mm difference is huge. Here is a 109 and a 156 (CE) compared, that is a big difference and it is certainly noticeable in use.



The 156 is primary and the 109 is secondary:

Okay, I'll have to challeng Nemrod a bit about this idea that "...ou cannot get O2 in if you cannot get CO2 out..." Research does not validate that statement. What causes the buildup of CO2, or "hypercapnia," is a low ventilation rate. Research does show that exhalation resistance can cause the diver to breathe shallower, thus decreasing the ventilation of the air sacs (alveoli).

The weight of evidence does not support increased ambient pressure as the cause of hypoventilation and hypercapnia seen with exercise at depth. While pres- sure itself may have some direct effects at very high pressures (e.g. 30 ATA) [37), breathing gas density (which increases in proportion to increases in pres- sure) is the most important factor in the development of hypoventilation and hypercapnia at the pressures ex- perienced by most recreational or commercial divers (typically up to ~6 ATA) [38]. Immersion, external breathing resistance from a regulator and hyperoxic breathing gas are also contributing factors.

Except for high inspired PCO2 in rebreather diving, hypercapnia occurs due to alveolar hypoventilation as a result of two main mechanisms: reduced total pul- monary ventilation — due to increased respiratory load and reduced chemosensitivity — and increased physiologic dead space. The following section elucidates these mechanisms and explores the possible impact of density-related gas exchange impairment and pressure-induced carbonic anhydrase inhibition on diving-related hypercapnia.

Respiratory load in the dive environment
Ventilation is a balance between chemosensitivity and ventilatory work [39,40]. Respiratory load — in- cluding elastic, resistive and inertial load — is in- creased in diving [41] and can lead to an increased work of breathing (WOB). Immersion, elevated gas density and external breathing resistance from a regulator all contribute to changes in respiratory load and exacerbate the increased WOB in diving. Immersion or submersion contributes to an increased WOB mainly through changes in lung elastic load. During immersion at any depth and in any posture, there is a passive redistribution of blood to the thorax and pulmonary vasculature. Pulmonary vascular en- gorgement occurs [42] resulting in an increase in lung elastic resistance [43] and necessitating higher negative inspiratory pressures [44].

https://dukespace.lib.duke.edu/dspace/bitstream/handle/10161/15586/Dunworth%20Hypercapnia%20in%20diving-a%20review%20of%20CO2%20retention%20in%20submersed%20exercise%20at%20depth%20Undersea%20Hyperb%20Med%202017.pdf?sequence=1

What this means is that the diver needs to be conscious of breathing, and continue to breathe deeply. Because of the slightly increased breathing resistance of the smaller exhaust, the tendency is to breathe shallower. This must be overcome by consciously breathing deeper. It is the shallow breathing, and the consequently decreased ventilation of the air sacs that the CO2 builds up. The tidal volume of most people is only about 0.5 liters, which is not much exchange. In diving, the respirations need to be deeper, so as to exchange a couple of liters of air during a breath (see the below diagram from the U.S. Navy Diving Manual, March 1970 about lung volumes). But many divers, especially divers experiencing either high inspiratory or expiratory breathing resistance, will involuntarily reduce the volume breathed, and thereby build up CO2 because it doesn't move the air out of the dead air spaces of the lungs (everything outside the air sacs).

This is why the very first regulators, the DA Aqualung, with high inspiratory levels of resistance, could adequately supply divers with air at depth; the divers breathed deeply, and the exhalation resistance was low (exhalation resistance in the old double hose regulators was low despite the design limitation of the valve for inhalation). It was not until the third generation of the Calypso regulator that the U.S. Naval EDU approved a single hose regulator, and the Voit MR-12 regulator also was approved.

I have been diving single hose regulators since the early 1960s, and have a collection of many of them with small diameter exhalation valves. I have dived those regulators without experiencing the symptoms of hypercapnia throughout my diving career.

SeaRat

 

[Nemrod]

Okay, I'll have to challeng Nemrod a bit about this idea that "...ou cannot get O2 in if you cannot get CO2 out..." Research does not validate that statement. What causes the buildup of CO2, or "hypercapnia," is a low ventilation rate. Research does show that exhalation resistance can cause the diver to breathe shallower, thus decreasing the ventilation of the air sacs (alveoli).



SeaRat

That is okay, y'all go ahead and use those regs with a dime sized exhaust valve, lol. There is a reason the dive equipment companies, all of them, went to 30mm valves.

Next time you are swimming laps I want you to inhale as normal but stick a straw in your mouth when you exhale and let me know how that goes for you. No cheating and exhaling through your nose.

 

[John C. Ratliff]

That is okay, y'all go ahead and use those regs with a dime sized exhaust valve, lol. There is a reason the dive equipment companies, all of them, went to 30mm valves.

Next time you are swimming laps I want you to inhale as normal but stick a straw in your mouth when you exhale and let me know how that goes for you. No cheating and exhaling through your nose.

You're not reading the entire post. Read again, and see what I'm really talking about, Nemrod. Yes, the larger exhausts are much, much better. But we did not experience hypercapnia because of the size of the exhaust, but the subsequent resistance and change in our respiratory reaction.

SeaRat

 

[Nemrod]

You're not reading the entire post. Read again, and see what I'm really talking about, Nemrod. Yes, the larger exhausts are much, much better. But we did not experience hypercapnia because of the size of the exhaust, but the subsequent resistance and change in our respiratory reaction.

SeaRat

No, I did not, the older I get the less my attention span is. It has gotten really short these days.


I know what is giving me a headache now!

 

[John C. Ratliff]

I knew you had not read the entire post, as I had not completed it before you replied.

By the way, the best exhalation resistance in a double hose regulator is my hybrid Healthways Scuba regulator, with the original Scuba exhaust (but with a double layer exhaust diaphragm) and no duckbill backup). That is really nice exhalation resistance.

On the single hose side, nothing can beat my Scubapro A.I.R. I for exhalation resistance, and I have been diving it since the 1980s.

SeaRat

PS, I think I’m older than you (I’m 77, going on 78 now).

 

[John C. Ratliff]

PJ Okinawa Dive003 by John Ratliff, on Flickr
Nemrod, my PJ buddies (and me) are pretty deep inside a coral reef off Okinawa in 1968, and are using those small exhalation valve Calypso regulators (USAF issue). They don’t look to be constrained at all by the small exhalation valve.

SeaRat