Info Some History of the NOAA Oxygen Limits

[tursiops]

It is popular on ScubaBoard to denigrate the NOAA Oxygen Exposure Limits, which were originally (from the NOAA Diving Manual 2nd Edition, 1979) given as:

The source of this table is clearly stated as the USNavy Diving Manual (1973).


By the NOAA Diving Manual 3rd Edition (1991) the limits had become:

The source of this info is clearly stated as from Butler and Thalmann (1986) and other data.

The 4th Edition (2001) of the NOAA Diving Manual gives:

The source is cited as:

The U.S. Navy has recently performed research on pure oxygen diving in exercising human volunteers. These investigations have shown, in a limited number of exposures, that substantially longer times appear to be possible for pure oxygen working dives than those given in Table 16.5, without the occurrence of oxygen convulsions (Butler and Thalmann 1984; Butler and Thalmann 1986; Butler 1986; Walters, Gould, Bachrach and Butler 2000); however, NOAA finds that the conservative limits established in this table are satisfactory for NOAA diving operations.​

Thus, NOAA clearly states that these are conservative limits and "that substantially longer times appear to be possible for pure oxygen working dives than those given in Table 16.5, without the occurrence of oxygen convulsions."

Butler reviewed all the US Navy work leading to this in 2004; see attached. He provided the first Oxygen Limits used by the USN, in 1954:

These are from NEDU Report 11-54.

(continued in next post)

 

[tursiops]

It is popular on ScubaBoard to denigrate the NOAA Oxygen Exposure Limits, which were originally (from the NOAA Diving Manual 2nd Edition, 1979) given as:
View attachment 877277
The source of this table is clearly stated as the USNavy Diving Manual (1973).


By the NOAA Diving Manual 3rd Edition (1991) the limits had become:
View attachment 877276
The source of this info is clearly stated as from Butler and Thalmann (1986) and other data.

The 4th Edition (2001) of the NOAA Diving Manual gives:
View attachment 877278
The source is cited as:

The U.S. Navy has recently performed research on pure oxygen diving in exercising human volunteers. These investigations have shown, in a limited number of exposures, that substantially longer times appear to be possible for pure oxygen working dives than those given in Table 16.5, without the occurrence of oxygen convulsions (Butler and Thalmann 1984; Butler and Thalmann 1986; Butler 1986; Walters, Gould, Bachrach and Butler 2000); however, NOAA finds that the conservative limits established in this table are satisfactory for NOAA diving operations.​

Thus, NOAA clearly states that these are conservative limits and "that substantially longer times appear to be possible for pure oxygen working dives than those given in Table 16.5, without the occurrence of oxygen convulsions."

Butler reviewed all the US Navy work leading to this in 2004; see attached. He provided the first Oxygen Limits used by the USN, in 1954:
View attachment 877280
These are from NEDU Report 11-54.

(continued in next post)

The next version of the Oxygen Exposure Limits appeared in the USN Diving Manual in 1959:

This was updated again in 2002:

For closure, the current USN Diving Manual Rev 7A (2018) gives:

So nothing has changed in the USN limits since 2002. The USN limits continue to reflect "exceptional exposure" limits, whereas the NOAA limits began in 1991 to diverge from showing both "Normal" and "Exceptional" limits so that in 2001 only normal limits were shown. There is a footnote on Table 15-1 from 1991 that says, "Exceptional exposures are for use only in lifesaving operations."

 

[rjack321]

A whole lot of lovely history sadly doesn't make them more predictive.

 

[tursiops]

A whole lot of lovely history sadly doesn't make them more predictive.

Some things are like that. It's been known for a century that toxicity is highly variable, even for the same individual. So the NOAA focus has been to provide working limits that are safe for most people in most situations. You are free to exceed those limits and welcome to accept the consequences of doing so.

You can also complain about the inadequacy of earthquake predictions, or snowfall at a particular location two weeks out, or how long you are going to live.

 

[Capt Jim Wyatt]

You can also complain about the inadequacy of earthquake predictions,

Where can I file that complaint?

 

[tursiops]

Where can I file that complaint?

Can you predict earthquakes? | U.S. Geological Survey

No. Neither the USGS nor any other scientists have ever predicted a major earthquake. We do not know how, and we do not expect to know how any time in the foreseeable future. USGS scientists can only calculate the probability that a significant earthquake will occur (shown on our hazard mapping)...

www.usgs.gov

I'd start with a tweet on the American Geophysical Union's Volcanology, Geochemistry, and Petrology site on X, or a letter to my Congressman complaining that the USGS and the NSF don't have enough money.

Or, I'd learn to pray.

 

[scubadada]

Thanks for the posts @tursiops

For quite a while, I have been interested in the NOAA 24-hour exposure limits with no credit until after the 24-hour period vs. several dive computers that utilize a 90-minute oxygen elimination half-life.

One of my dive computers since 2002 has been an Oceanic. Oceanic uses the NOAA 24-hour exposure limit without credit until after the 24-hour period. I often do 5 dives longer than an hour within a 24-hour period using 36% nitrox when diving from my home in Boynton Beach, FL. On several occasions I exceeded the NOAA 24-hour limit and the Oceanic computer alarmed.

In 2015 I added a Dive Rite Nitek Q and in 2019 I switched to a Shearwater Teric. Both of these computers use the 90-minute oxygen elimination half-life. Neither ever came close to the oxygen exposure limit while my Oceanic was over limit. Obviously, my Oceanic computer is more conservative than the Dive Rite or Shearwater. Most divers have no idea what I am talking about if I bring up the subject of oxygen exposure. See a post I made in 2016

Post in thread 'CNS exposure and deep diving'

Jun 19, 2016

Title: [abstract] A PROVISIONAL METHOD OF OXYGEN EXPOSURE MANAGEMENT FOR A RECREATIONAL DIVE COMPUTER
Author: Bohrer, CR; Hamilton, RW
Abstract: BACKGROUND: Increasing the fraction of oxygen in a breathing mixture effectively improves the efficiency of decompression. Unfortunately, oxygen is toxic in varying degrees depending upon the partial pressure and duration of the exposure. Various techniques have been suggested for managing a single oxygen exposure, but there is not yet available a mathematical algorithm usable in a dive computer (these have limited processing power and memory) or when...

• scubadada

• 

This is what Shearwater says in the Teric manual:

 

[tursiops]

For quite a while, I have been interested in the NOAA 24-hour exposure limits with no credit until after the 24-hour period vs. several dive computers that utilize a 90-minute oxygen elimination half-life.

I think the 90-minutes was a SWAG used by Bohrer and Hamilton in 1993 when they put together an algorithm for Seiko and Dive Rite.
See this interview with Lamar.

Lamar Hires -

www.tdisdi.com

I've not been able to locate the full referenced article (which may not exist because the citation is to the abstract):
Bohrer CR and Hamilton RW. A provisional method of oxygen exposure management for a recreational dive computer. Undersea Hyperbaric Med 1993; 20 (Suppl): 72.
Here is the abstract from the conference proceedings; the OCR was imperfect. I highlighted the relevant part:

A PROVISIONAL METHOD OF OXYGEN EXPOSURE MANAGEMENT FOR A RECREATIONAL DIVE COMPUTER. C. Randy Bohrer and R.W. Hamilton, Underwater Applications Corp., Nashua, NH, and Hamilton Research, Ltd., Tarrytown, NY. BACKGROUND: Increasing the fraction of oxygen in a breathing mixture effectively improves the efficiency of decompression. Unfortunately, oxygen is toxic in varying degrees depending upon the partial pressure and duration of the exposure. Various techniques have been suggested for managing a single oxygen exposure, but there is not yet available a mathematical algorithm usable in a dive computer (these have limited processing power and memory) or when developing tables that can account for multiple and multi-level exposures and for recovery between exposures. Even so, we needed a practical algorithm for use in a recreational dive computer that would warn the user when accepted limits were approached. METHODS: For limits we selected those in the 3rd edition of the NOAA Diving Manual. To deal with non-square exposures we used the interpolation method proposed by Kenyon and Hamilton (1989, XVth EUBS) which interpolates both O2 level and exposure time; this method tracks an Oxygen Limit Index (OLI), which is incremented at discreet time intervals by the ratio between the exposure time at the PO2) and the time limit for that PO2. A warning is issued when the ratio reaches 1.0, equivalent to the allowed time at a specific level. For recovery we used exponential decay, letting the OLI decrease with a half time of approximately 90 minutes when the PO2 is less than the established threshold of 0.5 atm. This allows 50% recovery in 1.5 hrs, 90% in 5, and full recovery in 9 hrs. Precise data to support this recovery rate is lacking, but it is consistent with the practice of intermittent oxygen breathing during hyperbaric therapy and the delay between repetitive treatments. RESULTS and CONCLIJSJON: The algorithm has been programmed into a new recreational dive computer, the Bridge, which has been developed by Dive Rite and Seiko. Random trials of "typical" exposures show that it appears to warn conservatively when presumably acceptable exposures are exceeded. but it allows dives that are regarded as having an acceptable oxygen exposure to be displayed without a warning.

 

[The Chairman]

It is popular on ScubaBoard to denigrate the NOAA Oxygen Exposure Limits,

Somehow, I must have missed all this denigration. I must admit to never having dove with enough frequency to have to cancel dives, as I plan that ahead of schedule.

 

[tursiops]

Somehow, I must have missed all this denigration. I must admit to never having dove with enough frequency to have to cancel dives, as I plan that ahead of schedule.

@PfcAJ