Hello dherbman:
2 ATA Limit (33 fsw)
I will make the guess that you are talking about recreational diving with scuba gear. In that case, as Diver0001 mentioned, you would not be able to stay at depth long enough to develop a problem. It requires many hours at shallow depths to load a sufficient dose of nitrogen.
Habitat Diving
There are individuals, e.g., marine scientists, who remain in a submersed habitat for many days. According to data publisged (see REFERENCES below), there is a possibility of DCS from depths much shallower than 33 fsw. This is, again, after days of exposure to pressure.
Dr Deco :doctor:
References :book3:
Eckenhoff RG, Osborne SF, Parker JW, Bondi KR. Direct ascent from shallow air saturation exposures. Undersea Biomed Res. 1986 Sep;13(3):305-16. (abridged for SCUBA BOARD)
Thirty-four healthy human subjects were exposed to shallow air saturation for 48 h [25.5 fsw, n = 19; 29.5 fsw. n = 15] and then decompressed to 1 ATA (0 fsw) in about 2 min. Symptoms included fatigue, limb and joint pain, headache, myalgias, and pruritus. No subject of 19 was diagnosed as having decompression sickness (DCS) after the shallower exposure, but 4 of 15 were diagnosed and treated for DCS subsequent to the deeper exposure. Almost all subjects in both groups had Doppler-detectable venous gas emboli (VGE) lasting up to 12 h postdecompression. Treated subjects had a recurrence of VGE several hours after the hyperbaric oxygen treatment. Only the duration of VGE, and not the VGE score, correlated with symptoms; and only the subjects body weight and age correlated with the VGE variables. This study indicates that hyperbaric air exposures of this magnitude are not as benign as previously thought.
Eckenhoff RG, Olstad CS, Carrod G. Human dose-response relationship for decompression and endogenous bubble formation. J Appl Physiol. 1990 Sep;69(3):914-8. (abridged for SCUBA BOARD)
The dose-response relationship for decompression magnitude and venous gas emboli (VGE) formation in humans was examined. Pressure exposures of 12, 16, and 20.5 ft of seawater gauge pressure were conducted in an underwater habitat for 48 h. The 111 human male volunteer subjects then ascended directly to the surface in less than 5 min and were monitored for VGE with a continuous-wave Doppler ultrasound device over the precordium or the subclavian veins at regular intervals for a 24-h period. No signs or symptoms consistent with decompression sickness occurred. However, a large incidence of VGE detection was noted. We conclude that the reduction in pressure necessary to produce bubbles in humans is much less than was previously thought. Fifty percent of humans can be expected to generate bubbles after decompression from a pressure exposure of only 11 ft of seawater. This may have significant implications for decompression schedule formulation and for altitude exposures that are currently considered benign. These results also imply that endogenous bubbles arise from preexisting gas collections.
