How do you calculate HASS capacity?

Multiply units per HASS load by available loads for gross capacity, then derate by chamber uptime and first-pass screen completion. 36 x 22 x 0.90 x 0.96 gives about 684 completed units.

What is the difference between HALT and HASS capacity?

HALT discovers design margins on small sample populations under extreme stress; HASS screens production units in larger loads at reduced stress. HASS capacity is therefore measured in units screened, not a few samples.

What is a good first-pass HASS completion rate?

A stable production screen should clear 95%+ first-pass; the default 96% means about 28.5 units per period need rerun. Falling first-pass completion is an early warning of a process excursion upstream.

Why does HASS chamber uptime matter so much?

Downtime scales directly with throughput. At 90% uptime the default loses 79.2 units to chamber downtime — far more than the 28.5 lost to reruns, making uptime the dominant constraint here.

How big should a HASS load be?

Units per load is set by fixture design and chamber volume while keeping every unit within the screen's thermal and vibration profile. Larger loads lift gross capacity but must not compromise uniformity across the fixture.

How do I raise completed HASS units?

Target the larger loss. In the default, the 79.2 units lost to downtime dwarf the 28.5 lost to reruns, so improving chamber uptime returns more completed units than chasing first-pass completion.

Environmental Test Chambers & Reliability Labs calculator

HASS Capacity Calculator

HASS capacity estimates how many production units a Highly Accelerated Stress Screen line can fully screen over a period, after losses to chamber downtime and units that fail the screen and need rerun. Quality and reliability engineers use it to commit ongoing screening throughput, match HASS capacity to production volume, and decide when a second chamber or larger fixtures are needed. Unlike HALT, HASS runs in production on larger loads, so the math is in units rather than a handful of samples. The breakdown of where units are lost shows whether uptime or screen completion is throttling your line.

What this calculator does

Estimate HASS screening capacity from units per screening load, available HASS loads, chamber uptime, and first-pass screen completion.
a lab scheduler needs to check whether HASS screening capacity covers the build plan
It computes completed HASS units by multiplying gross load capacity by chamber uptime and first-pass screen completion, and itemizes units lost to downtime and to rerun.

Formula used

Gross HASS capacity = units per HASS load × available HASS loads
Completed HASS units = gross capacity × HASS chamber uptime × first-pass screen completion

Inputs explained

Units per HASS load:
Available HASS loads:
HASS chamber uptime:
First-pass screen completion:

How to use the result

Use it to match HASS throughput against production volume, plan screening shifts, or find the constraint between chamber uptime and first-pass yield.
It assumes uptime and first-pass completion are stable averages; a process excursion that spikes failures or a chamber fault mid-shift will move actual throughput off the estimate.

Common questions

How do you calculate HASS capacity? Multiply units per HASS load by available loads for gross capacity, then derate by chamber uptime and first-pass screen completion. 36 x 22 x 0.90 x 0.96 gives about 684 completed units.
What is the difference between HALT and HASS capacity? HALT discovers design margins on small sample populations under extreme stress; HASS screens production units in larger loads at reduced stress. HASS capacity is therefore measured in units screened, not a few samples.
What is a good first-pass HASS completion rate? A stable production screen should clear 95%+ first-pass; the default 96% means about 28.5 units per period need rerun. Falling first-pass completion is an early warning of a process excursion upstream.
Why does HASS chamber uptime matter so much? Downtime scales directly with throughput. At 90% uptime the default loses 79.2 units to chamber downtime — far more than the 28.5 lost to reruns, making uptime the dominant constraint here.
How big should a HASS load be? Units per load is set by fixture design and chamber volume while keeping every unit within the screen's thermal and vibration profile. Larger loads lift gross capacity but must not compromise uniformity across the fixture.

Last reviewed 2026-05-12.