Hal's "get secretly high" clause in the Lung passage is a hardcover-stage insertion — the galleys have him descend and "exhale palely" without it.

This is material that was added after the early draft: absent from the 1993 manuscript, present in the published novel.

In the galley proofs. The 1995 galley proofs: …activate just one of the big exhaust fans and exhale palely… — no secret-tokes clause.

In the published book. Scene 13 (pp. 49–54; the p. 52 site)

Evidence. A single source reports this.

Bears on. This difference bears on the following open questions: what broke Hal if not (only) DMZ; damage vs. emergence.

Further notes. The explicit statement of Hal's secret highs in the Lung was added at the last stage — same authorial pattern as diff-cut-hal-drug-history in reverse: Wallace tuned exactly how much Hal-drug explicitness the text carries right up to press.