— Field Notes · Decompression Theory

The line you are allowed to cross

Bühlmann's M-value marks the tissue tension at which a compartment is deemed to have reached its tolerated limit. Gradient factors draw a more conservative line beneath it — GF Low governs the deep end of the ascent, GF High the surfacing point. Move the sliders and watch the permitted envelope narrow.

GF Low 30 %

GF High 85 %

Values at standard depths

Depth	Ambient (bar)	M-value (bar)	GF ceiling (bar)	Effective GF

Nitrogen tolerances from the Bühlmann ZH-L16C set. The gradient-factor line is drawn after Baker, Understanding M-values: GF Low is applied at the deep end of the plotted range (50 m), GF High at the surface, interpolated linearly between. Drawn for the fast TC 1b compartment (5 min half-time). Illustrative, not a dive plan.