Residual gas around a suspended sample carries heat in parallel with the sample itself. At high pressure the gas conducts like a continuum and pumping barely helps; once the molecular mean free path outgrows the gap, every decade of pressure buys a decade of relief. The knee between regimes depends on the gap size — drag it and watch the target pressure move, then read what fraction of the continuum the gas still owns.
Model: an ILLUSTRATIVE smooth interpolation g = 1/(1+pknee/p) between continuum-like and free-molecular limits, knee pressure ∝ 1/gap, with normalized coefficients — no specific gas, temperature or accommodation coefficient assumed, and the decade-per-decade decline holds only in the free-molecular asymptote. Real campaigns verify suppression experimentally via the length-series differential protocol. Schematic teaching tool, not an instrument.