I found a post by DocVikingo that may help to explain this dilemma.
"Diving nitrox to air tables bestows no demonstrated safety margin or edge.
While the lower N2 loading achieved by diving EAN to air tables may be theoretically appealing as a "safety factor," at present there simply is no corpus of scientific evidence for this. It has not been shown that diving nitrox is "safer" than diving air in the sense of reducing the risk of DCS, the severity of DCS or any other aspect of the sphere of DCI.
In fact, EAN is arguably less "safe" than air no matter what tables are being used. Several posters have raised the OxTox issue, and indeed diving nitrox greatly increases the likelihood of CNS oxygen toxicity if maximum operating depths or oxygen clock limitations are exceeded.
As DrDeco stated, "In practice, the incidence of DCS is very low in recreational diving." It is in fact so low that based on statistical considerations alone it would be a monumental undertaking to show a safety edge for EAN even if it did exist.
What diving EAN to air tables does do is reduce decompression obligations, required surface intervals & dive to fly times."
"Diving nitrox to air tables bestows no demonstrated safety margin or edge.
While the lower N2 loading achieved by diving EAN to air tables may be theoretically appealing as a "safety factor," at present there simply is no corpus of scientific evidence for this. It has not been shown that diving nitrox is "safer" than diving air in the sense of reducing the risk of DCS, the severity of DCS or any other aspect of the sphere of DCI.
In fact, EAN is arguably less "safe" than air no matter what tables are being used. Several posters have raised the OxTox issue, and indeed diving nitrox greatly increases the likelihood of CNS oxygen toxicity if maximum operating depths or oxygen clock limitations are exceeded.
As DrDeco stated, "In practice, the incidence of DCS is very low in recreational diving." It is in fact so low that based on statistical considerations alone it would be a monumental undertaking to show a safety edge for EAN even if it did exist.
What diving EAN to air tables does do is reduce decompression obligations, required surface intervals & dive to fly times."