Vacuum Decay (Blank-Off) Test

The evacuation standing-decay verdict: from the micron level at valve-off, the level after a timed hold, and the hold time, the total rise and the rise rate, with a tight-and-dry / moisture / leak reading against an editable 500-micron pass ceiling (ACCA Standard 4 / AHRI field practice).

rise_micron = end_micron - start_micron; rate_micron_per_min = rise / hold_min. Verdict: end at or below the pass ceiling (default 500 microns) is tight and dry; above it is residual moisture/outgassing if it plateaus or a leak if it climbs steadily.

First-principles standing-decay (blank-off) arithmetic (public); the 500-micron evacuation target and valve-off decay test are the common HVAC field convention (ACCA Standard 4 / AHRI / equipment manual, by name).

The rise/time arithmetic is public; the 500-micron pass ceiling is an editable field convention.

Estimate. AHJ and licensed professional govern.

Field names used by the API: start_micron, end_micron, hold_min, pass_ceiling_micron, rise_micron, rate_micron_per_min

• Pass ceiling default 500 microns at valve-off (editable); some manufacturers call for a deeper holdACCA Standard 4 / AHRI / equipment manual
• Moisture vs leak a rise that plateaus below ~1000-1500 microns is residual moisture/outgassing; a steady climb that does not plateau is a leakfield practice
• Instrument read with an electronic micron (vacuum) gauge isolated from the pump, not the manifold compound gaugefield practice