Ascent Rate in SSI Materials

[Dan G]

Reading the "Computer Diving" materials on SSI and it discusses ascent rate and how it relates to DCS. On the Inert Gas Elimination page the materials state that an ascent rate of 30 feet/per minute are necessary. My understanding has been that the limit is 60 ft/minute until a depth of 30 feet, when it changes to 30'/minute.

Has 30'/min always been the case? Is this new info or materials in need of an update?

 

[DiveProKoko]

Reading the "Computer Diving" materials on SSI and it discusses ascent rate and how it relates to DCS. On the Inert Gas Elimination page the materials state that an ascent rate of 30 feet/per minute are necessary. My understanding has been that the limit is 60 ft/minute until a depth of 30 feet, when it changes to 30'/minute.

Has 30'/min always been the case? Is this new info or materials in need of an update?

SSI Instructor here....the stated safe ascent rate for all recreational diving in SSI manuals is 30ft/minute, regardless of depth.

 

[rick00001967]

as far as i know ssi has always advocated for a 30ft/min ascent rate from any depth. keep in mind other agencies may have different standards.
i would add that i suggest to slow your ascent even further above 30 feet.
when i complete my 15ft safety stop for example, i would often take a couple of minutes to reach the surface from there if conditions allowed.

 

[Capt Jim Wyatt]

A long time ago 60 ft/minute was the prescribed ascent rate by the US Navy & recreational dive agencies used that benchmark. That rate was changed by the Navy to 30 ft/minute a few years ago & the agencies followed suit.

Rapid ascent rates are the leading cause of type 1 & 2 decompression sickness.

 

[TravisD]

I found the 2016 OW instructor manual in my archives, and 30fpm is the only mentioned ascent rate.

 

[Exxilon]

Reading the "Computer Diving" materials on SSI and it discusses ascent rate and how it relates to DCS. On the Inert Gas Elimination page the materials state that an ascent rate of 30 feet/per minute are necessary. My understanding has been that the limit is 60 ft/minute until a depth of 30 feet, when it changes to 30'/minute.

Has 30'/min always been the case? Is this new info or materials in need of an update?

As far as I can remember, the materials for computer diving indicate to follow the manufacturer's guidelines.

If you look at decompression protocols as related to technical diving then 10m/min is the norm over the entire industry. IMHO you don't need to make it more complicated than that.

Also, don't forget that the maximum is a *maximum*, not a goal!

Ascent rates *higher* than 10m/min are a maximum. In terms of the most common algorithms, an ascent rate of about 3m/min is the minimum required in order to facilitate any kind of objective oriented off gassing. 10m/min is, therefore, not a "rule" but an easy to remember "middle of the lane" number.

 

[boulderjohn]

I was certified in the last millennium. I planned to do it on vacation in Mexico. A friend loaned me her SSI OW manual to read ahead of time, and I studied it intently on my way. I then got certified by PADI, which had an ascent rate of no more than 60 FPM. I remember distinctly noting that as far as I could tell, that was the only difference between those courses. The SSI manual clearly said 30 FPM.

I only know of one agency that advocates different rates at different depths. There may be others I don't know about.

 

[Dan G]

Thanks for the replies. I recall learning in my mid-90s PADI OW cert 60'/min. My question comes from the fact that my Oceanic computer states 60'/min below 30' and then switches to 30'/min @ 30'. I don't own the data cable for the computer but I do plan to borrow one and update the firmware soon. I wonder if it will change this to 30'/min for all depths.

 

[boulderjohn]

Thanks for the replies. I recall learning in my mid-90s PADI OW cert 60'/min. My question comes from the fact that my Oceanic computer states 60'/min below 30' and then switches to 30'/min @ 30'. I don't own the data cable for the computer but I do plan to borrow one and update the firmware soon. I wonder if it will change this to 30'/min for all depths.

I can't speak for the Oceanic algorithm. Perhaps it will not change. There is evidence that ascents should be slower the closer you get to the surface, but there is not a lot of research to that effect.

 

[Angelo Farina]

Reading the "Computer Diving" materials on SSI and it discusses ascent rate and how it relates to DCS. On the Inert Gas Elimination page the materials state that an ascent rate of 30 feet/per minute are necessary. My understanding has been that the limit is 60 ft/minute until a depth of 30 feet, when it changes to 30'/minute.

Has 30'/min always been the case? Is this new info or materials in need of an update?

In the US Navy diving manual it was 60 fps up to around 1978, when they revised the manual, saying that 30 fps was the recommended ascent speed, but 60 was tolerated in case of emergency/need.