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Air Flow — Sensible heat (BTU / CFM / L/s / ΔT)

Air Flow tool step 1 — Sensible heat and duct pressure in one two-column grid. Prev / Next in the top bar switch to Fan Laws. Every box is typed; related values fill live.

• Grid is Imperial left, Metric right (BTU/kW, CFM/L/s, sq.in./cm², °F/°C, in. w.c./Pa, FPM/m/s). Dew and RH sit in a four-column row at the bottom. Type either box. No Calculate button. Formulas are in Help, not on the tool.
• The last box you commit (↵ or tap outside) is held. Every other box that a formula can compute from that new number is rewritten. Empty boxes with no formula stay empty. Area is typed only. Numpad C clears the focused field; it does not refill until you commit another box.
• CFM and L/s are the same volume (1 CFM ≈ 0.472 L/s). Type either when volume is an input. Volume-only does not invent BTU or ΔT.
• ΔT (°F) and ΔT (°C) are the same difference (Δ°C = Δ°F × 5/9 — 20 °C Δ is 36 °F Δ, not 68 °F). Type either when ΔT is an input.
• Settings °F/°C does not relabel these boxes. Formula (internal): BTU/hr = CFM × 1.08 × ΔT (°F). Changing CFM updates BTU, FPM, and VP when Area is set. Changing SP keeps TP and updates VP → FPM → CFM → BTU.

Disclaimer: Field guide for technicians — not a substitute for nameplate data or local Code.