Model CH₃OH spectra at different methanol-to-formaldehyde abundance ratios (colored dashed lines) compared to the ALMA CH₃ OH non-detections after Keplerian masking (gray) in the HD 163296 disk. Given the sensitivity levels achieved, the ALMA observations should be sensitive to the presence of methanol in the disk for CH₃ OH/H₂CO ≳ 0.2 based on the stacked band seven lines. Top panel: CH₃OH 1₁₀ –1₀₁ (A) line. Middle panel: CH₃OH 2₁₁ –2₀₂ (A) line. Bottom panel: stacked band seven CH₃OH lines.